Role of succinate dehydrogenase in hypoxic postconditioning-induced reduction of hypoxia-reoxygenation injury in myocardial cells of rats and the relationship with mito-K ATP / 中华麻醉学杂志

Objective:To evaluate the role of succinate dehydrogenase (SDH) in hypoxic postconditioning (HPC)-induced reduction of hypoxia-reoxygenation (H/R) injury in myocardial cells of rats and the relationship with mitochondrial ATP-sensitive potassium channels (mito-K ATP). Methods:Myocardial cells isolated from adult male Sprague-Dawley rats were cultured for 48 h and then divided into 7 groups ( n=24 each) using a random number table method: blank control group (Nor group), H/R group, SDHA-siRNA adenovirus+ H/R group (siRNA+ H/R group), HPC group, SDHA-siRNA adenovirus+ HPC group (siRNA+ HPC group), 5-HD+ HPC group, and SDHA-siRNA adenovirus+ 5-HD+ HPC group (siRNA+ 5-HD+ HPC group). Nor group was continuously cultured for 195 min under normoxic conditions. The H/R injury model was prepared by exposing the cells to hypoxia for 45 min in 5% CO 2 + 1% O 2 + 94% N 2, followed by reoxygenation for 150 min. The HPC method involved three cycles of 5 min reoxygenation/5 min hypoxia at the end of 45 min ischemia before 120 min reoxygenation. The mito-K ATP blocker 5-HD administration method involved adding 5-HD at a final concentration of 100 μmol/L at 30 min of hypoxia. The myocardial cells in each siRNA group were successfully transfected with SDHA-siRNA adenovirus to silence SDHA expression. The cell viability, calcium ion level, SDH activity, ATP content, degree of mitochondrial permeability transition pore (mPTP) opening, and mitochondrial membrane potential (MMP) were measured at the end of reoxygenation. Results:Compared with Nor group, the cell viability, ATP content and MMP were significantly decreased, and the degree of mPTP opening, level of calcium ion and activity of SDH were increased in H/R group ( P<0.05). Compared with H/R group, the cell viability, ATP content and MMP were significantly increased, and the degree of mPTP opening, calcium ion level and SDH activity were decreased in siRNA+ H/R group and HPC group ( P<0.05). Compared with HPC group, the cell viability, ATP content and MMP were significantly decreased, and the degree of mPTP opening, calcium ion level and SDH activity were increased in 5-HD+ HPC group ( P<0.05), and the cell viability, ATP content and MMP were significantly increased, and the degree of mPTP opening, calcium ion level and SDH activity were decreased in siRNA+ HPC group ( P<0.05). Compared with siRNA+ HPC group, the cell viability, ATP content and MMP were significantly decreased, the opening degree of mPTP and calcium ion level were increased ( P<0.05), and no significant change was found in the SDH activity in siRNA+ 5-HD+ HPC group ( P>0.05). Compared with 5-HD+ HPC group, the SDH activity was significantly decreased, and no significant change was found in the other parameters in siRNA+ 5-HD+ HPC group ( P>0.05). Conclusions:HPC alleviates H/R injury probably by reducing SDH activity and opening mito-K ATP in myocardial cells of rats.

Thoracic aortic reactivity in obese patients submitted to aerobic exercise / Reatividade da aorta torácica em pacientes obesos submetidos ao exercício aeróbico / Reactividad de la aorta torácica en pacientes obesos sometidos a ejercicio aeróbico

ABSTRACT Introduction: Aerobic exercise can improve the function of the cardiovascular circulatory system, reducing morbidity and mortality from cardiovascular disease by stimulating the production of endogenous self-protection. Activating potassium channels in vascular smooth muscle cells can cause vasodilation and increase blood flow, lowering blood pressure. There is a sensitivity to intracellular ATP and ADP concentration among the variety of potassium channels distributed in vascular smooth muscle cells, which vary mainly during aerobic physical activity. Objective: Explore the effect of aerobic exercise on the vascular reactivity of the thoracic aorta in patients with obesity and hyperlipidemia. Methods: Randomized controlled trial in twenty male Wistar rats weighing 250g and two months old. The control group remained at rest while the experimental group performed aerobic exercise on a treadmill at increasing speed for eight weeks. The rats were dissected, and dilatators and vasoconstrictors drugs stimulated their blood vessels in a tamponade solution. Observation of vascular changes was measured under controlled tensioning. Results: The blockade of KATP channels in vascular smooth muscle caused tonic contraction of vascular smooth muscle cells and increased blood pressure. Conclusion: Long-term regular aerobic exercise may induce changes in rats' thoracic aortic vascular function and vascular smooth muscle reactivity. Aerobic exercise can also significantly improve the activity of KATP channels. Evidence Level II; Therapeutic Studies - Investigating the results.

RESUMO Introdução: O exercício aeróbico pode melhorar a função do sistema circulatório cardiovascular, reduzindo a morbidade e mortalidade de doenças cardiovasculares estimulando a produção de autoproteções endógenas. A ativação de canais de potássio nas células musculares lisas vasculares pode causar vasodilatação e aumentar o fluxo sanguíneo, diminuindo a pressão sanguínea. Há uma sensível a concentração de ATP intracelular e ADP dentre a variedade de canais de potássio distribuídos em células musculares lisas vasculares, que variam principalmente durante a atividade física aeróbica. Objetivo: Explorar o efeito do exercício aeróbico na reatividade vascular da aorta torácica em pacientes com obesidade e hiperlipidemia. Métodos: Estudo randomizado controlado em vinte ratos Wistar machos de 250g e 2 meses de idade. O grupo controle permaneceu sob repouso enquanto o experimental realizava exercícios aeróbicos em esteira com velocidade crescente durante 8 semanas. Os ratos foram dissecados e seus vasos sanguíneos estimulados com drogas vasoconstritoras e dilatadoras em solução tampão. A observação das alterações vasculares foi mensurada sob tensionamento controlado. Resultados: O bloqueio dos canais KATP no músculo liso vascular causou contração tônica das células musculares lisas vasculares e aumento da pressão arterial. Conclusão: Exercícios aeróbicos regulares de longo prazo podem induzir alterações na função vascular da aorta torácica e reatividade do músculo liso vascular em ratos. O exercício aeróbico também pode melhorar significativamente a atividade dos canais KATP. Nível de evidência II; Estudos terapêuticos - investigação dos resultados do tratamento.

RESUMEN Introducción: El ejercicio aeróbico puede mejorar la función del sistema circulatorio cardiovascular, reduciendo la morbilidad y la mortalidad de las enfermedades cardiovasculares al estimular la producción de autoprotección endógena. La activación de los canales de potasio en las células del músculo liso vascular puede causar vasodilatación y aumentar el flujo sanguíneo, reduciendo la presión arterial. Existe una sensibilidad a la concentración intracelular de ATP y ADP entre la variedad de canales de potasio distribuidos en las células del músculo liso vascular, que varían principalmente durante la actividad física aeróbica. Objetivo: Explorar el efecto del ejercicio aeróbico sobre la reactividad vascular de la aorta torácica en pacientes con obesidad e hiperlipidemia. Métodos: Ensayo controlado aleatorio en veinte ratas Wistar macho de 250 g y 2 meses de edad. El grupo de control permaneció en reposo mientras que el grupo experimental realizó ejercicios aeróbicos en una cinta de correr a velocidad creciente durante 8 semanas. Las ratas fueron disecadas y sus vasos sanguíneos fueron estimulados con fármacos vasoconstrictores y dilatadores en solución amortiguada. La observación de los cambios vasculares se midió bajo tensión controlada. Resultados: El bloqueo de los canales KATP en el músculo liso vascular provocó una contracción tónica de las células del músculo liso vascular y un aumento de la presión arterial. Conclusión: El ejercicio aeróbico regular a largo plazo puede inducir cambios en la función vascular de la aorta torácica y en la reactividad del músculo liso vascular en ratas. El ejercicio aeróbico también puede mejorar significativamente la actividad del canal KATP. Nivel de evidencia II; Estudios terapéuticos - Investigación de resultados.

Role of sarcolemmal KATP channel in sevoflurane-induced maintenance of electrophysiological stabili-ty of ventricular myocardium in diabetic rats / 中华麻醉学杂志

Objective To evaluate the role of sarcolemmal ATP-sensitive potassium ( sarcKATP ) channel in sevoflurane-induced maintenance of electrophysiological stability of ventricular myocardium in di-abetic rats. Methods Clean-grade healthy male Sprague-Dawley rats, aged 3 months, weighing 280-320 g, in which diabetes mellitus ( DM) was induced by intraperitoneal streptozotocin 60 mg/kg and confirmed by blood glucose ≥16. 7 mmol/L, were used in this study. Their hearts were excised after anesthesia and retrogradely perfused in a Langendorff apparatus at 4 weeks after establishing the DM model. Twenty-four Langendorff-perfused hearts were divided into 3 groups ( n=8 each) using a random number table method:DM group ( group D) , DM plus sevoflurane group ( group DS) and DM plus sevoflurane plus HMR-1098 group (group DSH). Another 8 Langendorff-perfused hearts of normal rats were selected as control group ( group C) . Hearts were perfused with 37℃ K-H solution via the aorta in each group, 15 min of equilibra-tion later hearts were continuously perfused for 30 min with K-H solution in C and D groups, with K-H solu-tion saturated with 2. 5％ sevoflurane in group DS, or with K-H solution saturated with 10 μmol/L HMR-1098 and 2. 5％ sevoflurane in group DSH. Monophasic action potential (MAP) duration at 50％ and 90％repolarization ( MAPD50 and MAPD90 ) in the endocardium and epicardium of the left ventricular anterior wall were recorded at 15 min of equilibration ( T0 ) and 15 and 30 min of reperfusion ( T1,2 ) , transmural dispersion of repolarization ( TDR) was calculated. S1S2 program-controlled stimulation was performed at the end of perfusion to record the effective refractory period (ERP), ventricular arrhythmia (VA) induced and the longest pacing cycle length ( PCL) of ventricular fibrillation threshold ( VFT) induced. ERP/MAPD90 ratio was calculated. Results Compared with group C, TDR was significantly increased at T0 , ERP/MADP90 ratio was decreased, the incidence of VA induced was increased, and the longest PCL of VFT induced was prolonged in group D ( P＜0. 05) . Compared with group D, TDR was significantly decreased at T2 in group DS (P＜0. 05), and ERP/MADP90 ratio was significantly increased, the incidence of VA in-duced was decreased, and the longest PCL of VFT induced was shortened in DS and DSH groups ( P＜0. 05). TDR was significantly smaller at T2 in group DSH than in group DS (P＜0. 05). Conclusion sarcKATP channel is involved in sevoflurane-induced maintenance of electrophysiological stability of ventricu-lar myocardium in diabetic rats.

Role of mitochondrial ATP-sensitive potassium channels inurocot postconditioning-induced protection of rat cardiomyocytes / 中华麻醉学杂志

Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mito-KATP) channels in urocortin postconditioning-induced protection of rat cardiomyocytes.Methods Clean-grade healthy male Sprague-Dawley rats,aged 16-20 weeks,weighing 200-250 g,were used in this study.Cardiomyocytes of rats were isolated,cuhured and divided into 4 groups (n =28 each) using a random number table method:control group (group C),H/R group (group HR),urocortin postconditioning group (group U) and 5-hydroxydecanoate (5-HD,mito-KAw channel blocker) plus urocortin postconditioning group (group HU).In group C,the cells were continuously cultured for 150 min in an incubator filled with 95％ O2-5％ CO2 at 37 ℃.In group HR,the cells were exposed to 40-min hypoxia in an incubator filled with 95％ N2-5％ CO2 at 37 ℃,followed by 110-min reoxygenation.In group U,the cells were exposed to 40-min of hypoxia,followed by 10-min reoxygenation,and then cultured in a cuhure medium containing 10-8mmol/L urocortin for 30 min,followed by 70-min reoxygenation.In group HU,the cells were cultured for 10 min in a culture medium containing 10-4mmol/L 5-HD,and the other treatments were similar to those previously described in group U.At the end of reoxygenation,the opening of mitochondrial permeability transition pore (mPTP) and mitochondrial membrane potential (MMP) were measured by fluorescence spectrophotometry.The expression of Bax and Bcl-2 was determined by Western blot,and the cell viability was measured by CCK-8 assay.Results Compared with group C,the viability of cardiomyocytes and MMP were significantly decreased,the opening of mPTP was increased,the expression of Bcl-2 was down-regulated,and the expression of Bax was up-regulated in the other 3 groups (P＜0.05).Compared with group HR,the viability of cardiomyocytes and MMP were significantly increased,the opening of mPTP was decreased,the expression of Bcl-2 was up-regulated,and the expression of Bax was down-regulated in group U,and the opening of mPTP was decreased (P ＜ 0.05),and no significant change was found in the other parameters in group HU (P＞0.05).Compared with group U,the viability of cardiomyocytes and MMP were significantly decreased,the opening of mPTP was increased,the expression of Bcl-2 was down-regulated,and the expression of Bax was up-regulated in group HU (P＜0.05).Conclusion The mechanism by which urocortin postconditioning attenuates H/R-induced damage to rat cardiomyocytes is associated with promoting mito-KATP channel opening and inhibiting mPTP opening.

The research progress of mitoKATP in diabetes with cerebral ischemic injury / 天津医药

@#Diabetes is an important independent risk factor for cerebrovascular diseases. A large number of clinical and experimental studies have confirmed that diabetes can aggravate cerebral ischemic injury, but the mechanism is not yet clear. Mitochondrial ATP-sensitive potassium channel (mitoKATP) is an important ion channel located in the mitochondrial inner membrane, playing very important roles in many physiological and pathological processes. In recent years, studies have showed that mitoKATP has a protective effect on cerebral ischemic neuronal injury, but its protective mechanism is abolished in diabetes. The relationship between mitoKATP and diabetes with cerebral ischemic injury has attracted more and more attention. In this article, the role of brain mitoKATP in diabetes with cerebral ischemic injury was reviewed.

Role of mito-KATP channel in pinacidil postconditioning-induced reduction of myocardial ischemia-reperfusion injury in rats: an in vitro experiment / 中华麻醉学杂志

Objective To evaluate the role of mitochondrial KATP (mito-KATP) channel in pinacidil postconditioning-induced reduction of myocardial ischemia-reperfusion (I/R) injury in rats.Methods SPF healthy male Sprague-Dawley rats,aged 16-20 weeks,weighing 250-300 g,were anesthetized with pentobarbital.Their hearts were excised and perfused in a Langendorff apparatus with K-H solution saturated with 95％ O2-5％ CO2 at 36.5-37.5 ℃.Thirty-two Langendorff-perfused hearts were divided into 4 groups (n =8 each) using a random number table:control group (group C),group I/R,pinacidil postconditioning group (group P) and 5-hydroxy decanoic acid plus pinacidil postconditioning group (group 5-HD+P).Myocardial ischemia was induced by interrupting perfusion for 40 min followed by 60 min reperfusion.Immediately after onset of reperfusion,hearts were perfused with K-H solution containing 50 μmol/L pinacidil for 2 min and then with K-H solution for 58 min in group P,hearts were perfused with K-H solution containing 100 μmol/L 5-HD for 5 min,with K-H solution containing 50 μmol/L pinacidil for 2 min and then with K-H solution for 53 min in group 5-HD+P.The heart rate (HR),left ventricular developed pressure (LVDP),left ventricular end-diastolic pressure (LVEDP) and the maximum rate of increase in left ventricular pressure (+dp/dtmax) were recorded at 20 min of equilibration (T1) and at the end of reperfusion (T2).Myocardial tissues were obtained at T2 for determination of myocardial infarct size and for examination of myocardial ultrastructure and Flameng scoring of the mitochondria was performed.Results Compared with group C,the HR,LVDP and +dp/dtmax were significantly decreased,and the LVEDP,myocardial infarct size and mitochondrial Flameng score were increased at T2 in group I/R (P＜0.05).Compared with group I/R,the HR,LVDP and +dp/dtmax were significantly increased and the LVEDP,myocardial infarct size and mitochondrial Flameng score were decreased at T2 (P＜0.05),and the pathological changes of myocardium were significantly attenuated in group P,and no significant change was found in the parameters mentioned above in group 5-HD+P (P＞0.05).Compared with group P,the HR,LVDP and + dp/dtmax were significantly decreased and the LVEDP,myocardial infarct size and mitochondrial Flameng score were increased at T2 (P＜O.05),and the pathological changes of myocardium were accentuated in group 5-HD+P.Conclusion The whole mechanism by which pinacidil postconditioning reduces myocardial I/R injury is related to promoting opening of mito-KATP channel in rats.

Effects of corticotropin-releasing hormone on the expression of adenosine triphosphate-sensitive potassium channels (Kir6.1/SUR2B) in human term pregnant myometrium

OBJECTIVE: Corticotropin-releasing hormone (CRH) is a crucial regulator of human pregnancy and parturition. Adenosine triphosphate (ATP)-sensitive potassium (KATP) channels are important for regulating myometrial quiescence during pregnancy. We investigated regulatory effects of different concentrations of CRH on KATP channel expression in human myometrial smooth muscle cells (HSMCs) in in vitro conditions. METHODS: After treating HSMCs with different concentrations of CRH (1, 10, 102, 103, 104 pmol/L), mRNA and protein expression of KATP channel subunits (Kir6.1 and SUR2B) was analyzed by reverse transcription-polymerase chain reaction and western blot. We investigated which CRH receptor was involved in the reaction and measured the effects of CRH on intracellular Ca2+ concentration when oxytocin was administered in HSMCs using Fluo-8 AM ester. RESULTS: When HSMCs were treated with low (1 pmol/L) and high (103, 104 pmol/L) CRH concentrations, KATP channel expression significantly increased and decreased, respectively. SUR2B mRNA expression at low and high CRH concentrations was significantly antagonized by antalarmin (CRH receptor-1 antagonist) and astressin 2b (CRH receptor-2 antagonist), respectively; however, Kir6.1 mRNA expression was not affected. After oxytocin treatment, the intracellular Ca2+ concentration in CRH-treated HSMCs was significantly lowered in low concentration of CRH (1 pmol/L), but not in high concentration of CRH (103 pmol/L), compared to control. CONCLUSION: Our data demonstrated the regulatory effect was different when HSMCs were treated with low (early pregnancy-like) and high (labor-like) CRH concentrations and the KATP channel expression showed significant increase and decrease. This could cause inhibition and activation, respectively, of uterine muscle contraction, demonstrating opposite dual actions of CRH.

Role of mitochondrial ATP-sensitive potassium channel in reduction of myocardial ischemia-reperfusion injury by calcitonin gene-related peptide in rats : an in vitro experiment / 中华麻醉学杂志

Objective To evaluate the role of the mitochondrial ATP-sensitive potassium (mitoKATP) channel in reduction of myocardial ischemia-reperfusion (I/R) injury by calcitonin gene-related peptide (CGRP) in rats in an in vitro experiment.Methods Healthy adult male Sprague-Dawley rats,weighing 250-300 g,were used in this study.After the animals were anesthetized,their hearts were immediately removed and retrogradely perfused with oxygenated K-H solution at 37 ℃ in a Langendorff apparatus.Twenty-four isolated rat hearts were assigned into 4 groups (n =6 each) using a random number table:control group (C group),I/R group,CGRP group and 5-hydroxydecanoate (5-HD) group.The hearts were first perfused with K-H solution for 30 min in the three groups.The hearts were continuously perfused with K-H solution for 150 min in group C.The hearts were subjected to ischemia for 30 min followed by 120 min of reperfusion to establish the model of myocardial I/R injury.In group CGRP,after the hearts were perfused with K-H solution for 10 min,10-8 mol/L CGRP was infused for 20 min at a rate of 0.5 ml/min via the aorta,and then the model of myocardial I/R injury was established.In 5-HD group,specific mito-KATP channel blocker 5-HD 100 μmol/L was infused for 10 min at a rate of 0.5 ml/nin via the aorta,and the other treatments were similar to those previously described in CGRP group.At the end of equilibration and 30,60,90 and 120 min of reperfusion,heart rate (HR),left ventricular systolic pressure (LVSP),left ventricular end-diastolic pressure (LVEDP) and the maximum rate of increase or decrease in left ventricular pressure (±dp/dtmax) were recorded.The myocardial infarct size was measured by 2,3,5-triphenyltetrazolium chloride staining at 120 min of reperfusion.Results Compared with C group,HR,LVSP and ±dp/dtmax were significantly decreased and LVEDP was increased during reperfusion,and the percentage of myocardial infarct size was increased at 120 min of reperfusion in the other three groups (P＜0.05).Compared with I/R group,HR,LVSP and ±dp/dtmax were significantly increased and LVEDP was decreased during reperfusion,and the percentage of nyocardial infarct size was decreased at 120 min of reperfusion in CGRP group (P＜0.05).Compared with CGRP group,HR,LVSP and ±dp/dtmax were significantly decreased and LVEDP was increased during reperfusion,and the percentage of myocardial infarct size was increased at 120 min of reperfusion in 5-HD group (P＜0.05).Conclusion Opening of mito-KATP channels is involved in CGRP-iuduced reduction of myocardial I/R injury in rats in an in vitro experiment.

Role of mitochondrial ATP-sensitive potassium channels in dexmedetomidine-induced attenuation of myocardial ischemia-reperfusion injury in rats / 中华麻醉学杂志

Objective To evaluate the role of mitochondrial ATP-sensitive potassium(mito-KATP) channels in dexmedetomidine-induced attenuation of myocardial ischemia-reperfusion(I∕R)injury in rats. Methods Forty pathogen-free healthy male Sprague-Dawley rats, aged 8-12 weeks, weighing 200-350 g, were divided into 5 groups(n=8 each)using a random number table: sham operation group(group S), I∕R group, dexmedetomidine group(group DEX), a specific mito-KATPchannel blocker 5-hydroxyde-canoate(5-HD)group(group 5-HD)and dexmedetomidine plus 5-HD group(group DEX+5-HD). Myo-cardial I∕R was produced by occlusion of the anterior descending branch of the left coronary artery for 30 min followed by 120 min reperfusion in pentobarbital sodium-anesthetized rats. Dexmedetomidine 5 μg∕kg was intraperitoneally injected at 15 min prior to reperfusion in group DEX.5-HD 40 mg∕kg was intraperitoneally injected at 30 min prior to reperfusion in group 5-HD. In group DEX+5-HD, 5-HD 40 mg∕kg and dexme-detomidine 5 μg∕kg were intraperitoneally injected at 30 and 15 min prior to reperfusion, respectively. The parameters of cardiac function such as left ventricular systolic pressure(LVSP), left ventricular end-dias-tolic pressure(LVEDP)and the maximum rate of increase or decrease in left ventricular pressure(±dp∕dtmax)were recorded before ischemia(T0)and at 60 and 120 min of reperfusion(T1,2). Blood samples were collected from the carotid artery at the end of reperfusion for determination of the concentrations of cre-atine kinase-MB(CK-MB)and cardiac troponin I(cTnI)in serum. The animals were then sacrificed, and hearts were removed for determination of the myocardial infarct size in the left ventricular myocardial tissues. Results Compared with group S, the LVSP and ±dp∕dtmaxwere significantly decreased, and the LVEDP was increased at T1-2, and the concentrations of CK-MB and cTnI in serum and myocardial infarct size were increased in the other groups(P<0.05). Compared with group I∕R, the LVSP and ±dp∕dtmaxwere signifi-cantly increased, and the LVEDP was decreased at T1-2, and the concentrations of CK-MB and cTnI in ser-um and myocardial infarct size were decreased in group DEX, and the LVSP and ±dp∕dtmaxwere significant-ly increased at T1-2, the concentrations of CK-MB and cTnI in serum and myocardial infarct size were de-creased(P<0.05), and no significant change was found in LVEDP in group DEX+5-HD, and no signifi-cont change was found in the parameters mentioned above in group 5-HD(P>0.05). Compared with group DEX, the LVSP and ±dp∕dtmaxwere significantly decreased, and the LVEDP was increased at T1-2, and the concentrations of CK-MB and cTnI in serum and myocardial infarct size were increased in DEX+5-HD group(P<0.05). Conclusion The mechanism by which dexmedetomidine attenuates myocardial I∕R inju-ry is partially related to promotion of mito-KATPchannel opening in rats.

Effect of sevoflurane postconditioning on mitochondrial connexin 43 during myocardial ischemia-reperfusion in rats and the role of mito-KATP channels: an in vitro experiment / 中华麻醉学杂志

Objective To investigate the effect of sevoflurane postconditioning on mitochondrial connexin 43 (Cx43) during myocardial ischemia-reperfusion (I/R) in isolated rat hearts and the role of mitochondrial ATP-sensitive potassium (mito-KATP) channels in it.Methods Forty-five adult male SpragueDawley rats,weighing 200-250 g,were used in the study.Their hearts were excised and retrogradely perfused with K-H solution in a Langendorff apparatus.The 45 isolated hearts were assigned into 5 groups (n =9 each) using a random number table:control group (group C),I/R group,sevoflurane postconditioning group (group Sev),and sevoflurane postconditioning plus 5-hydroxydecanoate (5-HD,a specific mitoKATp channel blocker) group (group Sev+5-HD) and I/R plus 5-HD group (group I/R+5-HD).The hearts were subjected to 20 main of global ischemia followed by 90 min of reperfusion to establish the model of myocardial I/R injury.From the beginning of reperfusion,the hearts were perfused with K-H solution saturated with 3％ sevoflurane for 15 min in group Sev,with K-H solution saturated with 3％ sevoflurane and containing 100 μ mol/L 5-HD in group Sev+5-HD,and with K-H solution containing 100 μ mol/L 5-HD in group 5-HD.The heart rate (HR),left ventricular end-diastolic pressure (LVEDP),left ventricular developed pressure (LVDP) and the maximum rate of increase and decrease of ventricular pressure (±dp/dtmax) were recorded at the end of equilibration (T1) and 30 and 60 min of reperfusion (T2,3).At 90 min of reperfusion,the myocardial infarct size was measured by TTC staining,and the expression of total Cx43 (tCx43)and phosphorylated Cx43 (p-Cx43) in mitochondria was determined by Western blot analysis.The percentage of myocardial infarct size and p-Cx43/tCx43 ratio were calculated.Results Compared with group C,the HR,LVDP and ±dp/dtmax were significantly decreased,and the LVEDP was increased at T2,3,and the percentage of myocardial infarct size was increased in the other 4 groups,the expression of mitochondrial tCx43 and p-Cx43 was significantly down-regulated in I/R,Sev+5-HD and 5-HD groups (P＜0.05),and no significant change was found in the expression of mitochondrial tCx43 and p-Cx43 in group Sev (P＞0.05).Compared with group I/R,the HR,LVDP and ±dp/dtmax were significantly increased,and the LVEDP was decreased at T2,3,the percentage of myocardial infarct size was decreased,and the expression of mitochondrial tCx43 and p-Cx43 was up-regulated in group Sev (P＜0.05),and no significant change was found in the parameters mentioned above in Sev+5-HD and 5-HD groups (P＞0.05).Compared with group Sev,the HR,LVDP and ±dp/dt were significantly decreased,and the LVEDP was increased at T2,3,the percentage of myocardial infarct size was increased,and the expression of mitochondrial tCx43 and p-Cx43 was down-regulated in group Sev+5-HD (P＜0.05).There was no significant change in the pCx43/tCx43 ratio between the five groups (P＞0.05).Conclusion The mechanism by which sevoflurane postconditioning attenuates myocardial I/R injury may be related to induction of mito-KATP channel opening and up-regulation of the expression of mitochondrial Cx43 in cardiomyocytes of rats.

Effects of propofol on the mitochondria ATP-sensitive potassium channel that contains Kir6.2 and SUR1 subunits in rats with cerebral ischemia-reperfusion injury / 临床麻醉学杂志

Objective To evaluate the effects of propofol on the mitochondria ATP-sensitive potassium channel that contains Kir6.2 and SUR1 subunits in rats with cerebral ischemia-reperfusion injury.Methods Twenty-four male Sprague-Dawley rats,weighing 280-320g,were randomly divided into 3 groups (n = 8):sham operation group(group S),cerebral ischemia-reperfusion group (group IR)and propofol group (group P).Transient focal cerebral ischaemia and reperfusion injury was in-duced by middle cerebral artery occlusion model in group P and group IR.Rats in group P were injec-ted 50 mg/kg propofol 2hr prior to ischemia.In groups S and IR,1 ml of normal saline was injected instead.The neurological scores were evaluated and brain infarction size was measured using TTC-staining.The mRNA expression levels of Kir6.2 and SUR1 were analyzed by quantitative polymerase chain reaction,while the protein levels of Kir6.2 and SUR1 were determined by western blot analysis. Results Compared with group S,neurological scores and infarction size was increased in group IR and group P,and the mRNA and protein levels of Kir6.2 in the group IR were down-regulated(P <0.05).Compared with group IR,neurological scores and infarction size decreased and the mRNA and protein levels of Kir6.2 were up-regulated in group P(P < 0.05 );the expressions of SUR1 in the three groups showed no significant difference.Conclusion Propofol could attenuate cerebral ischemia and reperfusion injury through up-regulating Kir6.2 expression in rats.

Influence of Thromboxane A₂ on the Regulation of Adenosine Triphosphate-Sensitive Potassium Channels in Mouse Ventricular Myocytes

BACKGROUND AND OBJECTIVES: Adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels play an important role in myocardial protection. We examined the effects of thromboxane A₂ on the regulation of K(ATP) channel activity in single ventricular myocytes. SUBJECTS AND METHODS: Single ventricular myocytes were isolated from the hearts of adult Institute of Cancer Research (ICR) mice by enzymatic digestion. Single channel activity was recorded by excised inside-out and cell-attached patch clamp configurations at -60 mV holding potential during the perfusion of an ATP-free K-5 solution. RESULTS: In the excised inside-out patches, the thromboxane A₂ analog, U46619, decreased the K(ATP) channel activity in a dose-dependent manner; however, the thromboxane A₂ receptor antagonist, SQ29548, did not significantly attenuate the inhibitory effect of U46619. In the cell-attached patches, U46619 inhibited dinitrophenol (DNP)-induced K(ATP) channel activity in a dose-dependent manner, and SQ29548 attenuated the inhibitory effects of U46619 on DNP-induced K(ATP) channel activity. CONCLUSION: Thromboxane A₂ may inhibit K(ATP) channel activity, and may have a harmful effect on ischemic myocardium.

Influence of Thromboxane A₂ on the Regulation of Adenosine Triphosphate-Sensitive Potassium Channels in Mouse Ventricular Myocytes

BACKGROUND AND OBJECTIVES: Adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels play an important role in myocardial protection. We examined the effects of thromboxane A₂ on the regulation of K(ATP) channel activity in single ventricular myocytes. SUBJECTS AND METHODS: Single ventricular myocytes were isolated from the hearts of adult Institute of Cancer Research (ICR) mice by enzymatic digestion. Single channel activity was recorded by excised inside-out and cell-attached patch clamp configurations at -60 mV holding potential during the perfusion of an ATP-free K-5 solution. RESULTS: In the excised inside-out patches, the thromboxane A₂ analog, U46619, decreased the K(ATP) channel activity in a dose-dependent manner; however, the thromboxane A₂ receptor antagonist, SQ29548, did not significantly attenuate the inhibitory effect of U46619. In the cell-attached patches, U46619 inhibited dinitrophenol (DNP)-induced K(ATP) channel activity in a dose-dependent manner, and SQ29548 attenuated the inhibitory effects of U46619 on DNP-induced K(ATP) channel activity. CONCLUSION: Thromboxane A₂ may inhibit K(ATP) channel activity, and may have a harmful effect on ischemic myocardium.

Role of atp-dependent k channels in the effects of erythropoietin in renal ischaemia injury.

Background & objectives: Erythropoietin (EPO) has cytoprotective and anti-apoptotic effects in pathological conditions, including hypoxia and ischaemia-reperfusion injury. One of the targets to protect against injury is ATP-dependent potassium (KATP ) channels. These channels could be involved in EPO induced ischaemic preconditoning like a protective effect. We evaluated the cell cytoprotective effects of EPO in relation to KATP channel activation in the renal tubular cell culture model under hypoxic/normoxic conditions. Methods: Dose and time dependent effects of EPO, KATP channel blocker glibenclamide and KATP channel opener diazoxide on cellular proliferation were evaluated by colorimetric assay MTT [3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide] under normoxic and hypoxic conditions in human renal proximal tubular cell line (CRL-2830). Evaluation of the dose and time dependent effects of EPO, glibenclamide and diazoxide on apoptosis was done by caspase-3 activity levels. Hypoxia inducible factor-1 alpha (HIF-1 α) mRNA levels were measured by semi-quantative reverse transcription polymerase chain reaction (RT)-PCR. Kir 6.1 protein expresion was evalutaed by western blot. Results: Glibenclamide treatment decreased the number of living cells in a time and dose dependent manner, whereas EPO and diazoxide treatments increased. Glibenclamide (100 μM) treatment significantly blocked the anti-apoptotic effects of EPO (10 IU/ml) under both normoxic and hypoxic conditions. EPO (10 IU/ml) and diazoxide (100 μM) treatments significantly increased (p<0.01) whereas glibenclamide decreased (p<0.05) HIF-1 α mRNA expression. Glibenclamide significantly (p<0.01) decreased EPO induced HIF-1 α mRNA expression when compared with the EPO alone group. Interpretation & conclusions: Our results showed that the cell proliferative, cytoprotective and anti-apoptotic effects of EPO were associated with KATP channels in the renal tubular cell culture model under hypoxic/normal conditions.

Cardioprotective effects of atorvastatin postconditioning on ischemia-reperfusion injury in isolated rat heart:the role of PI3K-Akt, mito-KATP channel and mPTP / 天津医药

Objective To observe the postconditioning cardioprotective effects of atorvastatin (ATV) on ischemia-re?perfusion injury in isolated rat heart, and the role of phosphatidylinositol-3-kinase , protein kinase B(PI3K-Akt), mitochon?drial ATP-sensitive potassium (mito-KATP channel) and mitochondrial permeability transition pore (mPTP) thereof. Meth?ods Healthy male Wistar rats were randomly divided into 9 groups:ischemia reperfusion (I/R) control group, atorvastatin postconditioning (ATV) group, ATV plus PI3K inhibitor LY294002 (ATV+LY294002) group, LY294002 group, ATV plus mi?to-KATP channel inhibitor 5-hydroxydecanoate (ATV+5-HD) group, 5-HD group, ATV plus mPTP inhibitor ATR (ATV+ATR) group, ATR group and ethanol group. Model rats were given 30-min ischemia followed by 120-min reperfusion. The myocardial infarction size, hemodynamic parameters, creatine kinase isoenzyme (CK-MB), lactate dehydrogenase (LDH), nic?otinamide adenine dinucleotide (NAD+) and the expression of myocardial protein kinase B (Akt) and myocardial phospho-pro?tein kinase B (p-Akt) were evaluated. Results Compared with the control group, atorvastatin reduced the myocardial in?farction size, CK-MB and LDH(P<0.05), increased NAD+(P<0.05). There were no significant differences in the myocardi?al infarction size, CK-MB, LDH and NAD+between ATV+LY294002 group, ATV+5-HD group and ATV+ATR group. The hemodynamic parameters were improved in ATV group compared with those in control group. Western blot analysis con? firmed the significant phosphorylation of Akt in ATV group, ATV+5-HD group and ATV+ATR group compared with those of control group. There were no significant differences in the phosphorylation of Akt between ATV +LY294002 group, LY294002 group, ATR group and 5-HD group. Conclusion Atorvastatin postconditioning could attenuate the ischemia-re?perfusion injury through activating the PI3K-Akt, promoting mito-KATP channel opening and inhibiting mPTP opening.

Role of mitochondrial ATP-sensitive potassium channel in mitigation of cerebral ischemia-reperfusion injury by isoflurane preconditioning in rats: the relationship with JNK signaling pathway / 中华麻醉学杂志

Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mitoKATP) channel in mitigation of cerebral ischemia-reperfusion (I/R) injury by isoflurane preconditioning in rats and the relationship with c-Jun N-terminal kinase (JNK) signaling pathway.Methods Thirty-two male Sprague-Dawley rats,weighing 280-320 g,were randomly divided into 4 groups (n =8 each) using a random number table:sham operation group (group S),group I/R,isoflurane preconditioning group (group Ⅰ-pre),and 5-hydroxydecanoate (5-HD,a selective mitoKATP channel antagonist) group.Cerebral I/R was produced by modified 4-vessel technique described by Pulsinelli in anesthetized rats.In group Ⅰ-pre,the rats were exposed to 1.5％ isoflurane for 1 h everyday for 5 consecutive days before ischemia.In group 5-HD,5-HD 15 mg/kg was injected intraperitoneally at 30 min before ischemia and the other procedures were similar to those previously described in group Ⅰ-pre.Neurological behavior was evaluated at 24 h of reperfusion.The rats in each group were sacrificed at 72 h of reperfusion,and the brains were removed for determination of neuronal apoptosis (by TUNEL) and expression of caspase-3 and phosphor-JNK (p-JNK) protein (using Western blot) in hippocampal tissues.Apoptotic rate was calculated.Results Compared with group S,the number of grid cross was significantly decreased,hanging time was shortened,apoptotic rate was increased,and caspase-3 expression was up-regulated in I/R,Ⅰ-pre and 5-HD groups,the expression of p-JNK protein was up-regulated in IR and 5-HD groups,and no significant change was found in the expression of p-JNK protein in group Ⅰ-pre.Compare with group I/R,the number of grid cross was significantly increased,hanging time was prolonged,apoptotic rate was decreased,and the expression of caspase-3 and p-JNK protein was downregulated in group Ⅰ-pre,and no significant change was found in the parameters mentioned above in group 5-HD.Compared with group Ⅰ-pre,the number of grid cross was significantly decreased,hanging time was shortened,apoptotic rate was increased,and the expression of caspase-3 and p-JNK protein was up-regulated in group 5-HD.Conclusion The mitoKATP channel is involved in mitigation of cerebral I/R injury by isoflurane preconditioning through blocking the JNK signaling pathway in rats.

Exercise and adenosine triphosphate-sensitive potassium channel / 中国组织工程研究

BACKGROUND:In the condition of exercise physiology, adenosine triphosphate-sensitive potassium (KATP) channel plays an important role in many aspects, such as regulation of coronary artery tension, exercise-induced myocardial protection effect and delay of skeletal muscle fatigue. OBJECTIVE:To review and investigate the role of KATP in exercise in order to provide theoretical reference for understanding mechanism underlying exercise regulation of body’s metabolism. METHODS: A computer-based online search of PubMed and VIP databases was performed for articles related to molecular structure, biological function and regulatory role of KATP as wel as correlation of KATP with coronary artery, myocardium, skeletal muscle fatigue and exercise ability published from January 1991 to June 2014. The keywords were “KATP channels; adenosine triphosphate; sports; myocardium; ion channels” in English and Chinese, respectively. Finaly, 42 relevant articles were included in result analysis. RESULTS AND CONCLUSION: Coupling with celular energy metabolism and cel membrane excitability, KATP channel is one of the effectors for myocardial protection in response to various physiological and pathological stresses. Prolonged endurance training can increase the expression of skeletal muscle and myocardial KATP, which may be an adaptive performance of the myocardium and skeletal muscle in response to exercise stress. KATP may participate in regulation of coronary blood flow. Myocardial KATP plays an important protective role for aleviating myocardial ischemia-reperfusion injury induced by exercise. When skeletal muscle fatigue occurs, the activation of KATP is helpful to prevent muscle fiber damage and cel death due to excessive consumption of ATP, in favor for the fast recovery from fatigue. The relation between KATP and exercise ability stil needs further research.

Role of mitochondrial ATP-sensitive potassium channels in attenuation of cerebral ischemia-reperfusion injury by dexmedetomidine in rats / 中华麻醉学杂志

Objective To evaluate the role of mitochondrial ATP-sensitive potassium (mito-KATe) channels in attenuation of cerebral ischemia-reperfusion (I/R) injury by dexmedetomidine in rats.Methods One hundred and twenty healthy male Wistar rats,weighing 290-340 g,were randomly assigned into 5 groups (n =24 each) using a random number table:sham operation group (group S) ; group I/R; dexmedetomidine group (group D) ; 5-HD (a specific blocker of mito-KATPchannel) group and 5-HD + dexmedetomidine group (group 5-HD + D).The rats were anesthetized with intraperitoneal chloral hydrate.Focal cerebral I/R was produced by 2 h middle cerebral artery occlusion followed by reperfusion.In group D,dexmedetomidine 50 μg/kg was injected intraperitoneally before ischemia and after onset of reperfusion.In group 5-HD,5-HD 30 mg/kg was injected intraperitoneally at 1 h before ischemia.In 5-HD + D group,5-HD 30 mg/kg was injected intraperitoneally at 1 h before ischemia and the other procedures were similar to those previously described in group D.Twelve rats were chosen at 24 and 48 h of reperfusion to assess the neurological deficit score (NDS).The animals were then sacrificed and brains were removed for determination of cerebral infarct size by TTC staining.Results Compared with S group,NDS and cerebral infarct size were significantly increased at each time point in the other four groups (P ＜ 0.05).Compared with group I/R,NDS and cerebral infarct size were significantly decreased in D and 5-HD + D groups (P ＜ 0.05),and no significant change was found in the parameters mentioned above in 5-HD group (P ＞ 0.05).Compared with group D,NDS and infarct size were significantly increased in group 5-HD + D (P ＜ 0.05).Conclusion Mito-KATP channels are involved in reduction of I/R-induced cerebral injury by dexmedetomidine in rats.

Effect of Simvastatin on ATP-sensitive K+ channels and L-type Ca2+ channels in mouse pancreatic beta cells / 中华老年医学杂志

Objective To observe the influence of Simvastatin on the ATP-sensitive K+Channels and L-type Ca2+ Channels in mouse pancreatic beta cell line MIN6.Methods MIN6 cells were divided into 0.05 ％ dimethyl sulfoxide (DMSO) group,normal control group and low-,middle-,high-concentration of Simvastatin treatment groups,that were cultured for 48 h with high-glucose DMEM containing 15％ fetal bovine serum plus 0.05％ dimethyl sulfoxide,0,2,5 and 10 μmol/Lsimvastatin,respectively.Whole-cell patch-clamp technology was used to record the currents of ATP-sensitive K+ channels and L-type Ca2+ channels in MIN6 cells.Results The mean potassium current density in normal external solution perfusion group was (92.81 ±4.10) pA/pF.Compared with normal external solution perfusion control group,2,5 and 10 μmol/L Simvastatin treatments markedly enhanced the current density of ATP-sensitive K+ Channels,reaching to (117.94 ± 3.67)pA/pF,(153.91±12.38) pA/pF,(307.01±6.40) pA/pF (all P＜0.01),respectively.The current density in L-type Ca2+ Channels was (-21.03 ± 0.55) pA/pF in glucose external solution group.Compared with glucose external solution group,the current density in 2,5 and 10 μmol/L Simvastatin treatment groups were decreased to (16.31±0.51) pA/pF,(-10.75±0.71) pA/pF,(-3.30±0.46) pA/pF (all P＜0.01),respectively.Conclusions Simvastatin inhibits insulin secretion and glycometabolism in mouse pancreatic beta cell line MIN6 via enhancing the current density of ATP-sensitive K+ Channels and inhibiting the current density of L-type Ca2+ Channels.

Molecular mechanisms of ischemic preconditioning mediated neuroprotection / 国际脑血管病杂志

A large number of animal experiments have confirmed that ischemic preconditioning can produce a powerful organ protective effect,but the progress and results of the conversion of animal experiments to clinical trials are unsatisfactory.It has great significance for studying of molecular mechanisms of ischemic preconditioning mediated neuroprotection,searching for safe and effective preconditioning induced ways which can be converted to clinical practice,improving the tolerance of nerve tissue ischemia and hypoxia in stroke and surgical patients and achieving a safe and effective neuroprotection.This article reviews the molecular mechanisms of ischemic preconditioning mediated neuroprotection from the aspects of pretreatment of activated receptor,mitochondria,transcription factor,and protein kinase.