Dapagliflozin regulates myocardial SK2 protein expression in diabetic rats / 中国药理学通报

Aim To investigate the effect of dapagliflozin on the small conductance calcium-activated potassium channel 2 (SK2 channel) protein in the myocardium of diabetic rats and its possible mechanism of action. Methods In vivo: type 2 diabetes model was established by high-glucose and high-fat diet combined with intraperitoneal injection of low-dose streptozotocin (35 mg

Effect of Zhenwu Decoction on electrical remodeling of cardiomyocytes in heart failure via I_(to)/Kv channels / 中国中药杂志

This study aimed to investigate the underlying mechanism of Zhenwu Decoction in the treatment of heart failure by regulating electrical remodeling through the transient outward potassium current(I_(to))/voltage-gated potassium(Kv) channels. Five normal SD rats were intragastrically administered with Zhenwu Decoction granules to prepare drug-containing serum, and another seven normal SD rats received an equal amount of distilled water to prepare blank serum. H9c2 cardiomyocytes underwent conventional passage and were treated with angiotensin Ⅱ(AngⅡ) for 24 h. Subsequently, 2%, 4%, and 8% drug-containing serum, simvastatin(SIM), and BaCl_2 were used to interfere in H9c2 cardiomyocytes for 24 h. The cells were divided into a control group [N, 10% blank serum + 90% high-glucose DMEM(DMEM-H)], a model group(M, AngⅡ + 10% blank serum + 90% DMEM-H), a low-dose Zhenwu Decoction-containing serum group(Z1, AngⅡ + 2% drug-containing serum of Zhenwu Decoction + 8% blank serum + 90% DMEM-H), a medium-dose Zhenwu Decoction-containing serum group(Z2, AngⅡ + 4% drug-containing serum of Zhenwu Decoc-tion + 6% blank serum + 90% DMEM-H), a high-dose Zhenwu Decoction-containing serum group(Z3, AngⅡ + 8% drug-containing serum of Zhenwu Decoction + 2% blank serum + 90% DMEM-H), an inducer group(YD, AngⅡ + SIM + 10% blank serum + 90% DMEM-H), and an inhibitor group(YZ, AngⅡ + BaCl_2 + 10% blank serum + 90% DMEM-H). The content of ANP in cell extracts of each group was detected by ELISA. The relative mRNA expression levels of ANP, Kv1.4, Kv4.2, Kv4.3, DPP6, and KChIP2 were detected by real-time quantitative PCR. The protein expression of Kv1.4, Kv4.2, Kv4.3, DPP6, and KChIP2 was detected by Western blot. I_(to) was detected by the whole cell patch-clamp technique. The results showed that Zhenwu Decoction at low, medium, and high doses could effectively reduce the surface area of cardiomyocytes. Compared with the M group, the Z1, Z2, Z3, and YD groups showed decreased ANP content and mRNA level, increased protein and mRNA expression of Kv4.2, Kv4.3, DPP6, and KChIP2, and decreased protein and mRNA expression of Kv1.4, and the aforementioned changes were the most notable in the Z3 group. Compared with the N group, the Z1, Z2, and Z3 groups showed significantly increased peak current and current density of I_(to). The results indicate that Zhenwu Decoction can regulate myocardial remodeling and electrical remodeling by improving the expression trend of Kv1.4, Kv4.2, Kv4.3, KChIP2, and DPP6 proteins and inducing I_(to) to regulate Kv channels, which may be one of the mechanisms of Zhenwu Decoction in treating heart failure and related arrhythmias.

Antiarrhythmic active components in traditional Chinese medicine acting on potassium channels / 中国中药杂志

Arrhythmia is an external manifestation of cardiac electrophysiological disorder. It exists in healthy people and patients with various heart diseases, which is often associated with other cardiovascular diseases. The contraction and diastole of myocardium are inseparable from the movement of ions. There are many ion channels in the membrane and organelle membrane of myocardium. The dynamic balance of myocardial ions is vital in maintaining myocardial electrical homeostasis. Potassium ion channels that have a complex variety and a wide distribution are involved in the whole process of resting potential and action potential of cardiomyocytes. Potassium ion channels play a vital role in maintaining normal electrophysiological activity of myocardium and is one of the pathogenesis of arrhythmia. Traditional Chinese medicine(TCM)has unique advantages in treating arrhythmia for its complex active components and diverse targets. A large number of TCM preparations have definite effect on treating arrhythmia-related diseases, whose antiarrhythmic mechanism may be related to the effect on potassium channel. This article mainly reviewed the relevant studies on the active components in TCM acting on different potassium channels to provide references for clinical drug use and development.

Remifentanil Down-regulates GIRK2 Expression in Rat Dorsal Root Ganglion and Spinal Dorsal Horn / 中山大学学报(医学科学版)

ObjectiveTo observe the changes in the expression and distribution of G protein-gated inwardly rectifying potassium channel subunit 2 （GIRK2） in the dorsal root ganglion （DRG） and spinal cord dorsal horn of rats with remifentanil-induced hyperalgesia. MethodsHyperalgesia was induced by intravenous infusion of remifentanil 4 μg/kg/min for 2 h in adult male SD rats. At 6th hour and on days 1， 3 and 5 following remifentanil treatment， we used immunofluorescence to examine the changes in the GIRK2 distribution and expression. Immunoblotting was used to detect GIRK2 expression of the total protein and membrane protein in DRG and spinal dorsal horn of rats. Behavioral testing was applied to evaluate the effect of intrathecal injection of GIRK2-specific agonist ML297 on thermal nociceptive threshold on day 1 after remifentanil infusion. Resultsmmunofluorescence results showed that GIRK2 was mainly co-localized with IB4-positive small neurons in DRG and nerve fibers in spinal dorsal horn. GIRK2 expression was significantly downregulated following remifentanil treatment. Immunoblotting results revealed that on day 1 following intravenous infusion of remifentanil， compared with those in the control group， GIRK2 expression levels of the total protein and membrane protein in DRG （0.47 ± 0.10 vs. 1.01 ± 0.17， P < 0.001； 0.47 ± 0.11 vs. 1.06 ± 0.12， P < 0.001） and spinal dorsal horn （0.52 ± 0.09 vs. 1.10 ± 0.08， P < 0.001； 0.54 ± 0.10 vs. 1.01 ± 0.13， P < 0.001） were all significantly decreased. The behavioral results showed that intrathecal ML297 effect on thermal withdrawal latency was significantly reduced following remifentanil treatment （P < 0.001）. ConclusionsRemifentanil might induce hyperalgesia via down-regulating GIRK2 expression in rat DRG and spinal cord dorsal horn.

The insulinotropic effects and its relevant mechanism of telmisartan in rats / 中国药理学通报

Aim To investigate the insulinotropic effect of telmisartan anrl the underlying electrophysiological mechanism.Methods Islets and cells were isolated from Wistar rats.Islets were incubated with drugs un¬der different conditions, then supernatant liquid was collected for insulin secretion.Intracellular Ca" + ( Ca'+ j) levels of (3-cells were measured by calcium imaging technology.Patch-clamp technology was ap¬plied to detect effects on voltage-gated potassium chan¬nel ( Kv ) , and voltage-gated calcium channel ( VGCC ).Results Not affecting insulin secretion un¬der low glucose condition, telmisartan dose-dependent- ly stimulated insulin secretion under high glucose con¬ dition, and stimulation was enhanced with increasing glucose concentration.Acute increases of Ca' + concentration were elicited by telmisartan under high glucose condition.Telmisartan decreased current den¬sity of Kv channel, and increased VGCC current densi¬ty.Conclusions Telmisartan enhanced Ca~+ ; lev¬els of p-cells through its action on Kv channel and VGCC, thereby amplifying glucose-stimulated insulin secretion.

Effect of Shuangshen Ningxin Capsule in Alleviating Myocardial Ischemia/Reperfusion Injury in Rats by Regulating Mitochondrial ATP-sensitive Potassium Channel / 中国实验方剂学杂志

Objective:To observe the effect of Shuangshen Ningxin capsule in alleviating myocardial ischemia/reperfusion injury in rats by regulating mitochondrial adenosine triphosphate（ATP）-sensitive potassium channels.Method:A total of 56 adult male Sprague-Dawley rats were randomly divided into sham-operated control group (sham), model group (model), Shuangshen Ningxin group (SSNX, 90 mg·kg-1).Shuangshen Ningxin and mitochondrial ATP-sensitive potassium channel (MitoKATP) channel inhibitor group 5-hydroxyl-acid group (SSNX+5-HD, 5 mg·kg-1), with 14 rats in each group. Except the sham operation group, the other three groups received occlusion of left anterior descending coronary artery (LAD) for 45 min, and were sacrificed 3 h after reperfusion. Myocardial ischemia and infarct size were observed by TSC Evans blue staining, and myocardial tissue damage degree was observed by hematoxylin-eosin(HE) staining. The kit was used to measure serum lactate dehydrogenase (LDH), creatine kinase (CK) and creatine kinase isoenzyme (CK-MB). The ultrastructural changes of mitochondria and mitochondrial autophagy were observed under transmission electron microscope. The changes of mitochondrial membrane potential in cardiomyocytes were detected by fluorescent probe.Result:Compared with the sham group, myocardial infarct size and myocardial ischemic area percentage in the model group were significantly increased, myocardial tissue arrangement was disordered and loose, individual myocardial fibers were broken, cardiomyocytes were necrotic, and serum CK, CK-MB, LDH activities were significantly increased (P<0.01). Mitochondrial membrane potential was significantly decreased (P<0.01), and mitochondrial structure was destroyed by transmission electron microscopy. Compared with the model group, the myocardial tissue of the SSNX group was arranged orderly, and a small amount of cell edema was mildly degenerated. The percentage of myocardial infarct size and myocardial ischemic area was significantly decreased, serum CK, CK-MB, and LDH activities were significantly decreased (P<0.01), while mitochondrial membrane potential increased (P<0.01). Compared with the model group, the SSNX+5-HD group had mild myocardial tissue disorder and mild degeneration of cell edema in some areas, the percentage of myocardial infarct size and myocardial ischemic area was significantly reduced, serum CK, CK-MB, and LDH activities were significantly decreased (P<0.01), and mitochondrial membrane potential increased (P<0.01). Compared with SSNX group, SSNX+5-HD group had significant increase in serum CK, CK-MB and LDH activities (P<0.01), significant increase in the percentage of myocardial infarct size and myocardial ischemic area, and mitochondrial membrane potential Reduced (P<0.05).Conclusion:SSNX protects rat myocardial ischemia-reperfusion injury by opening mitochondrial ATP-sensitive potassium channel.

Progress in understanding the central nervous system pharmacology of the two-pore domain potassium channel TREK-1 / 药学学报

Two-pore domain potassium channels (K2P) make up a subfamily of potassium channels discovered in the 1990s, and TREK-1 is the most widely studied subtype of K2P. TREK-1 is widely expressed in the body and especially in the central nervous system, where its main role is to control cell excitability and maintain the membrane potential below the depolarization threshold. It thereby participates in regulating various physiological and pathological processes. TREK-1 is also a potential drug target in many diseases. It is known that many marketed drugs can affect the function of TREK-1, but currently there are no specific TREK-1 modulators or drugs. We review the structure, distribution and regulation of TREK-1 and focus on recent progress in understanding the pharmacology of TREK-1 and its role in neuroprotection, depression, anesthesia and epilepsy. The research status of TREK-1 modulators is discussed.

Decreased inward rectifier and voltage-gated K⁺ currents of the right septal coronary artery smooth muscle cells in pulmonary arterial hypertensive rats

In vascular smooth muscle, K⁺ channels, such as voltage-gated K⁺ channels (Kv), inward-rectifier K⁺ channels (Kir), and big-conductance Ca²⁺-activated K⁺ channels (BK(Ca)), establish a hyperpolarized membrane potential and counterbalance the depolarizing vasoactive stimuli. Additionally, Kir mediates endothelium-dependent hyperpolarization and the active hyperemia response in various vessels, including the coronary artery. Pulmonary arterial hypertension (PAH) induces right ventricular hypertrophy (RVH), thereby elevating the risk of ischemia and right heart failure. Here, using the whole-cell patch-clamp technique, we compared Kv and Kir current densities (I(Kv) and I(Kir)) in the left (LCSMCs), right (RCSMCs), and septal branches of coronary smooth muscle cells (SCSMCs) from control and monocrotaline (MCT)-induced PAH rats exhibiting RVH. In control rats, (1) I(Kv) was larger in RCSMCs than that in SCSMCs and LCSMCs, (2) I(Kv) inactivation occurred at more negative voltages in SCSMCs than those in RCSMCs and LCSMCs, (3) I(Kir) was smaller in SCSMCs than that in RCSMCs and LCSMCs, and (4) I(BKCa) did not differ between branches. Moreover, in PAH rats, I(Kir) and I(Kv) decreased in SCSMCs, but not in RCSMCs or LCSMCs, and I(BKCa) did not change in any of the branches. These results demonstrated that SCSMC-specific decreases in I(Kv) and I(Kir) occur in an MCT-induced PAH model, thereby offering insights into the potential pathophysiological implications of coronary blood flow regulation in right heart disease. Furthermore, the relatively smaller I(Kir) in SCSMCs suggested a less effective vasodilatory response in the septal region to the moderate increase in extracellular K⁺ concentration under increased activity of the myocardium.

Study on Vasodilatory Effect of Oxysophocarpine on Isolated Thoracic Aortic Rings of Rats and Its Mechanism / 中国药房

OBJECTIVE： To study the vasodilatory effect of oxysophocarpine （OSC） on isolated thoracic aortic rings of rats and its possible mechanism. METHODS： Thoracic aortic rings of rats were collected （called “vascular ring” for short）. Using K-H nutrient solution as blank control and the diastolic rate as index， the effects of different concentrations （0.2-1.0 mg/mL） of OSC on normal vascular rings in basal state， normal or endothelium-free vascular rings pre-contracted by norepinephrine （PE， 1×10－6 mol/L） were investigated. After pre-culturing normal thoracic aortic rings by nitric oxide synthase inhibitor L-nitro-arginine methyl ester（L-NAME）and cyclooxygenase inhibitor indomethacin（INDO），as well as pre-culturing endothelium-free vascular rings by potassium ion channel blocker BaCl2，tetraethylammonium（TEA）and 4-aminopyridine（4-AP）， the diastolic effects of OSC of different concentrations （0.2-1.0 mg/mL） on the above vascular rings were investigated by using the same method. RESULTS： Compared with blank control， there was no significant effects of different concentrations of OSC on the diastolic rate of normal vascular rings in basal state （P＞0.05）， but 0.4-1.0 mg/mL OSC could significantly improve the diastolic rate of normal or endothelium-free vascular rings pre-contracted by PE （P＜0.01）， in concentration-dependent manner. After preculturing with L-NAME， INDO， 4-AP and BaCl2， different concentrations of OSC had no significant effect on the diastolic rate of normal or endothelium-free vascular rings pre-contracted by PE （P＞0.05）. After pre-culturing with TEA and Gli， 0.4-1.0 mg/mL OSC could significantly reduce the diastolic rate of endothelium-free vas- cular rings pre-contracted by PE （P＜0.01）. CONCLUSIONS： OSC did not significantly dilate the thoracic aortic rings of rats in the basal state within the dose range （0.2-1.0 mg/mL）， but OSC of 0.4-1.0 mg/mL have significant diastolic effects on the normal or endothelium-free thoracic aortic rings of rats pre-contracted with PE. The mechanism of thoracic aortic rings dilation is endothelium-independent， which may be associated with receptor operational calcium channel，Ca2+-activated potassium channels and ATP-sensitive potassium channels.

Study on the Vasodilatory Effect Mechanism of Psoralen and Bakuchiol / 中国药房

OBJECTIVE： To investigate the vasodilatory effect mechanism of psoralen and bakuchiol. METHODS： The rat thoracic aorta was isolated to prepare vascular rings and de-endothelium vascular rings. Using contraction rate as index， the intact endothelium or de-endothelium vascular rings were pre-incubated with N-nitro-L-arginine methyl ester （L-NAME， 100 μmol/L）； vasodilatory effect of low-dose， medium-dose and high-dose of psoralen or bakuchiol（0.1，1，10 μmol/L）on aortic vessels pre- contracted with norepinephrine （NE， 1 μmol/L） or potassium chloride （KCl， 60 mmol/L） were investigated. The de-endothelium vascular rings were pre-incubated with calcium dependent potassium channel inhibitors tetraethylammonium chloride （TEA， 0.1 mmol/L） and inward rectifying potassium channel inhibitor barium chloride （BaCl2，0.1 mmol/L）； vasodilatory effect of low-dose， medium-dose and high-dose of bakuchiol （0.1， 1， 10 μmol/L） on de-endothelium vascular vessels pre-contracted with NE （1 μmol/L） were investigated. The microvascular endothelial cells were isolated by collagenase-neutral protease digestion； the effects of low-dose， medium-dose and high-dose of psoralen or bakuchiol （0.1， 1， 10 μmol/L） on the expression of eNOS protein were studied by ELISA. RESULTS： Psoralen and bakuchiol could significantly reduce the contraction rate of endothelium-intact aortic rings pre-contracted with NE（P＜0.01）； medium-dose and high-dose of psoralen and bakuchiol could significantly reduce the contraction rate of  endothelium-intact aortic rings pre-contracted with KCl（P＜0.05 or P＜0.01）； while the contraction rate could be increased by de-endothelium and NOS inhibition significantly （P＜0.05 or P＜0.01）. The medium-dose and high-dose of bakuchiol could significantly reduce the contraction rate of  de-endothelium vascular vessels pre-contracted with NE （P＜0.05 or P＜0.01）. The contraction rate could be increased by inhibiting inward rectifier potassium channels in vascular smooth muscle （P＜0.01）. Different dosages of psoralen and bakuchiol could significantly increase the expression levels of eNOS protein in rat cardiac microvascular endothelial cells（P＜0.01）. CONCLUSIONS： Psoralen and bakuchiol may play a role in vasodilation via endothelium-dependent NO pathway and by promoting eNOS protein expression in endothelial cells； bakuchiol may play a role in vasodilation via non-endothelium dependent pathway as opening inward rectifying potassium channel.

Effect of protease activated receptor 2 on colonic motility in diabetes mice / 上海交通大学学报（医学版）

Objective • To observe the effect of protease activated receptor 2 (PAR2) on the colonic motility in diabetic mice and investigate the mechanism. Methods • The mouse model of type 1 diabetes mellitus was established by intraperitoneal injection of streptozotocin. The smooth muscle strips and segments of colons were isolated. The effects of PAR2 agonist on colonic motility were observed by muscle strip tension contraction and colonic migrating motor complex experiments. The effect of small conductance calcium-activated potassium channel (SK3 channel) antagonist on it was also observed. Results • PAR2 agonist inhibited colonic motility and colonic smooth muscle was more sensitive to PAR2 agonist in diabetic mice. PAR2 agonist-induced inhibition was inhibited by SK3 channel antagonist. Conclusion • PAR2 activity in diabetic mice colons is significantly enhanced, which may inhibit colonic motility through SK3 channel.

Antitussive effect and mechanism study of effective fractions from Sauropus rostratus / 中草药

Objective: To study the antitussive effect of Sauropus spatulifolius, screen the active part of its antitussive effect, and study its antitussive mechanism. Methods The acute toxicity of different extraction sites of S. spatulifolius were studied by modified Karber’s method; The model was made with ammonia liquor to induce cough. The spray time that caused half of the mice to cough was calculated by sequential method with aim to screen the active sites. Capsaicin was used to induce cough, and the mechanism of action of extracts from various parts of S. spatulifolius on opioid receptor and ATP-sensitive potassium channel (KATP) of mice was explored. Results The LD50 of 75% ethanol, ethyl acetate, n-butanol, and 95% ethanol extracts was 7.30, 17.00, 69.68, and 75.88 g/kg, respectively; The maximum tolerance dose (MTD) of petroleum ether extracts was 117.71 g/kg; Extracts from 75% ethanol and ethyl acetate had antitussive effects, and its antitussive effect was related to opioid receptor and KATP pathway. Conclusion The fractions from 75% ethanol and ethyl acetate are the active parts of S. spatulifolius for relieving cough, and its antitussive mechanism is related to the KATP pathway and opioid receptors in the excited central system.

Construction of stable cell lines expressing large conductance Ca2+-activated K+ channel α-subunit and molecular mechanism of potassium excretion in this channel / 上海交通大学学报（医学版）

Objective: To construct stable cell lines expressing the large conductance Ca2+-activated K+ channel (MaxiK or BK) α-subunit and to explore the mechanism of potassium excretion via BKα channel. Methods:The BKα plasmid with Myc tag was constructed and transfected into HEK293 cell lines by lipofectamine 2000. The positive monoclonal cell lines were screened by G418, and the expression of BKα was detected by Western blotting and the location of BKα by immunofluorescence. The stable cell lines expressing BKα protein was cultured on slides to form a single cell layer, which was perfused with different potassium ion concentrations of 5 mmol/L and 100 mmol/L, and the single channel patch clamp recorded the ion flux of BKα. Wild type and mutants (G77R, G130R, C140R and R297C) of the inwardly rectifying potassium channel (Kir4.1) were transfected into HEK293 cells stably transfected with BKα, and then the membrane protein was extracted. The expression of BKα was detected by Western blotting. Results:Stable cell lines expressing BKα channel were selected from HEK293 cells after transfection and cellular immunofluorescence verified the expression of BKα channel and its expression on the cell membrane. The channel open frequency (Npo) of BKα increased rapidly when perfused with 100 mmol/L potassium. After being transfected with wild type or mutants of Kir4.1, the membrane expression of BKα in the stable cell lines showed significant difference among these groups (P<0.05). Conclusion:The HEK293 cell lines stably expressing BKα have been successfully constructed. BKα channel can be activated by high potassium solutions. The function of the BKα subunit can be related to Kir4.1 channel, which may be attributed to the depolarization of the cells transfected by Kir4.1 mutants.

Expression of KCNA2 in the dorsal root ganglia of rats with osteoarthritis pain induced by monoiodoacetate / 南方医科大学学报

OBJECTIVE@#To investigate the changes in the expression of voltage-gated potassium channel subunit KCNA2 in the dorsal root ganglion (DRG) neurons of rats with osteoarthritis (OA) pain induced by sodium monoiodoacetate and explore the mechanism.@*METHODS@#A total of 156 adult male Sprague-Dawley rats were randomly divided into blank control group, saline group and intra-articular monoiodoacetate injection-induced OA group. The paw withdrawal mechanical threshold (PWMT) was measured before and at 1, 2, 4, and 6 weeks after monoiodoacetate injection. At 4 weeks after the injection, the pathological changes in the knee joints were analyzed using HE staining and Safranin O-Fast Green staining, and the expression of activating transcription factor 3 (ATF-3) and inducible nitric oxide synthase (iNOS) in the DRG neurons were detected by immunofluorescence staining. The expression of mRNA in the DRG neurons was detected by RT-qPCR at 1, 2, 4 and 6 weeks after the injection. The expression of KCNA2 in the DRG was measured by Western blotting, and the methylation level of promoter region was measured by MSPCR at 4 weeks after the injection.@*RESULTS@#The PWMT of the rats in OA group was significantly decreased at 2, 4, and 6 weeks after the injection as compared with the baseline ( < 0.05 or < 0.001) as well as the control group ( < 0.05 or < 0.001). Four weeks after the intra-articular injection, fractures and defects on the surface of the articular cartilage, bone hyperplasia, and blurred tidal line were observed in the rats in OA group, but no obvious pathological changes were detected in the control or saline groups. Compared with those in the control group, the expressions of ATF-3 and iNOS were significantly increased ( < 0.01) at 4 weeks after injection; the expression of mRNA at 2, 4 and 6 weeks and the expression of KCNA2 protein at 4 weeks were all significantly decreased ( < 0.05 or < 0.01), and the methylation level of gene was significantly increased at 4 weeks after the injection in OA group ( < 0.01).@*CONCLUSIONS@#The expression of KCNA2 is decreased in the DRG neurons of rats with OA pain likely as a result of enhanced methylation of promoter region.

The Effects of 4-Hydroxybenzoic Acid Identified from Bamboo (Dendrocalamus asper) Shoots on Kv1.4 Channel

Background: Bamboo shoot has been used as a treatment for epilepsy in traditional Chinese medicine for generations to treat neuronal disorders such as convulsive, dizziness and headaches. 4-hydroxybenzoic acid (4-hba) is a non-flavonoid phenol found abundantly in Dendrocalamus asper shoots (bamboo), fruits (strawberries and apples) and flowers. Kv1.4 is a rapidly inactivating Shaker-related member of the voltage-gated potassium channels with two inactivation mechanisms; the fast N-type and slow C-type. It plays vital roles in repolarisation, hyperpolarisation and signaling the restoration of resting membrane potential through the regulation of the movement of K+ across the cellular membrane. Methods: Chemical compounds from Dendrocalamus asper bamboo shoots were purified and identified as major palmitic acids mixed with other minor fatty acids, palmitic acid, 4-hydroxybenzaldehyde, lauric acid, 4-hydroxybenzoic acid and cholest-4-ene-3-one. The response of synthetic 4-hydroxybenzoic acid was tested on Kv1.4 potassium channel which was injected into viable oocytes that was extracted from Xenopus laevis. The current were detected by the two-microelectrode voltage clamp, holding potential starting from −80 mV with 20 mV stepup until +80 mV. Readings of treatments with 0.1% DMSO, 4-hba concentrations and K channel blockers were taken at +60 mV. The ratio of tail/peak amplitude is the index of the activity of the Kv1.4 channels with n ≥ 6 (number of oocytes tested). The decreases of the ratios of five different concentrations (1 μM, 10 μM, 100 μM, 1 mM and 2.5 mM) were compared with 0.1% DMSO as the control. Results: All concentration showed statistically significant results with P < 0.05 except for 100 μM. The normalised current of the 4-hba concentrations were compared with potassium channel blockers (TEA and 4-AP) and all groups showed statistically significant results. This study also showed that time taken for each concentration to affect Kv1.4 does not play any significant roles. Conclusion: 4-hydroxybenzoic acid was found to be able to enhance the inactivation of Kv1.4 by lowering the membrane potential so that the abnormal neuronal firing can be inhibited. With IC50 slightly higher than 10 μM, increasing concentrations (100 μM, 1 mM and 2.5 mM) had shown to exhibit toxicity effects. The best concentration from this study is 10 μM with Hill slope of 0.1799.

13,14-EpDPE dilates coronary arterioles in rats by activating BK channels / 医学研究生学报

Objective The mechanisms of docosahexaenoic acid (DHA) protecting the cardiovascular system have not yet been clarified. This study was to investigate the vasorelaxative effect of 13,14-epoxy docosapentaenoic acid (13,14-EpDPE) on coronary arterioles in normal rats and its action mechanisms.Methods We isolated coronary artery smooth muscle cells (CASMCs) from normal rats by enzyme digestion, examined the open probabilities of the large conductance calcium-activated potassium (BK) channels in inside-out single channel configuration in the presence of different concentrations (0, 1, 10 and 100 pmol/L) of 13,14-EpDPE, and recorded the BK currents with the patch clamp in whole cell configuration. Then we assessed the coronary arterial relaxation by measuring dilatory responses to 13,14-EpDPE in pre-contracted tissues with or without pre-treatment with iberiotoxin.Results In the presence of 0, 1, 10 and 100 pmol/L of 13,14-EpDPE, the open probabilities of the BK channels were 0.25±0.03, 0.34±0.03, 0.44±0.06 and 0.85±0.16 (n=6), respectively, significantly increased at 100 pmol/L as compared with 0, 1 and 10 pmol/L (P<0.05). The BK channels were activated by 13,14-EpDP in a concentration-dependent manner and its half-effect concentration was (15.94±1.21) pmol/L. The current density was increased from (58.27±16.35) to (95.94±23.00) pA/pF (P=0.002) after 10 pmol/L 13,14-EpDP perfusion when the stimulation voltage was 100 mV. 13,14-EpDPE dilated the isolated coronary arterioles in a dose-dependent manner, and its effects were abolished after pre-treatment with iberiotoxin (100 nM).Conclusion 13,14-EpDPE can dilate coronary arterioles by activating BK channels in CASMCs, which might be one of the mechanisms underlying its protective effect on the cardiovascular system.

Research progress in the role of aquaproin-4 and inward rectifying potassium channel 4.1 in spinal cord edema / 中南大学学报(医学版)

Spinal edema is a very important pathophysiological basis for secondary spinal cord injury,which affects the repair and prognosis of spinal cord injury.Aquaporin-4 is widely distributed in various organs of the body,and is highly expressed in the brain and spinal cord.Inward rectifying potassium channel 4.1 is a protein found in astrocytes of central nervous system.It interacts with aquaporins in function.Aquaporin-4 and inward rectifying potassium channel 4.1 play an important role in the formation and elimination of spinal cord edema,inhibition of glial scar formation and promotion of excitotoxic agents exclusion.The distribution and function of aquaporin-4 and inward rectifying potassium channel 4.1 in the central nervous system and their expression after spinal cord injury have multiple effects on spinal edema.Studies of aquaporin-4 and inward rectifying potassium channel 4.1 in the spinal cord may provide new ideas for the elimination and treatment of spinal edema.

Effect of down-regulation of IKs repolarization-reserve on ventricular arrhythmogenesis in a guinea pig model of cardiac hypertrophy / 中南大学学报(医学版)

Objective:To observe the changes of rapidly activated delayed rectifier potassium channel (IKs) and slowly activated delayed rectifier potassium channel (IKs) in cardiac hypertrophy and to evaluate the effects of IKs and IKs blocker on the incidence ofventricular arrhythmias in guinea pigs with left ventricular hypertrophy (LVH).Methods:Guinea pigs were divided into a sham operation group and a left ventricular hypertrophy (LVH) group.LVH model was prepared.Whole cell patch-clamp technique was used to record IKr and IKs tail currents in a guinea pig model with LVH.The changes of QTc and the incidence rate of ventricular arrhythmias in LVH guinea pigs were observed by using the IKr and IKs blockers.Results:Compared with cardiac cells in the control group,the interventricular septal thickness at end systole (IVSs),left ventricular posterior wall thickness at end systole (LVPWs),QTc interval and cell capacitance in guinea pigs with LVH were significantly increased (P＜0.05);while IKs densities were significantly reduced [+60 mV:(0.36±0.03) pA/pF vs (0.58±0.05) pA/pF,P＜0.01].However,LVH exerted no significant effect on IKr densities.IKr blocker markedly prolonged the QTc interval (P＜0.01) and increased the incidence of ventricular arrhythmias in guinea pigs with LVH compared with the control guinea pigs.In contrast,IKs blocker produced modest increase in QTc interval in guinea pigs of control group with no increase in LVH animals.IKs blocker did not induce ventricular arrhythmias incidence in either control or LVH animals.Conclusion:The cardiac hypertrophy-induced arrhythmogenesis is due to the down-regulation of IKs.

Changes of two-pore K+ channel TASK-1 in diabetic myocardial injury in rats / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the changes of the two- pore K channel TASK-1 in diabetic rats with myocardial injury.</p><p><b>METHODS</b>Thirty-six SD rats were divided into normal group (N), diabetes at 4 weeks (DM 4W) group, and diabetes at 8 weeks (DM 8W) group. The cardiac functions of the rats were determined using cardiac ultrasonography, and the body weight and heart weight of the rats at different time points were measured to calculate the heart/body weight ratio (HW/BW). Myocardial fibrosis in the rats was assessed using Masson's staining. The protein expression of TASK-1 in the myocardium was detected using Western blotting. Whole- cell patch clamp technique was used to record the action potential duration (APD) and twopore domain potassium channel TASK- 1 current in acutely isolated rat ventricular myocytes. meanwhile, The inhibition of TASK-1 current was observed by the TASK-1 specific inhibitor ML-365.</p><p><b>RESULTS</b>Compared with the normal group, the diabetic rats showed significantly increased HW/BW ( < 0.05), end- diastole left ventricular diameter (LVIDd), end- systolic left ventricular diameter (LVIDs), and TASK-1 protein expression, with obviously decreased left ventricular diameter shortening rate (FS) and ejection fraction (EF) ( < 0.01). Masson staining showed that in diabetic rats, the collagen fibers were thickened, interwoven into a network with uneven arrangement and increased deposition. Compared with DM 4W group, the rats in DM 8W group exhibited progressive increases in LVIDd, LVIDs, HW/BW, and TASK-1 expression ( < 0.01 or 0.05); FS and EF were further decreased ( < 0.01). Masson staining showed worsened morphological changes of the myocardium with increased deposition. Compared with that in the normal group, the current of TASK- 1 in diabetic rats at 8 weeks was significantly reduced ( < 0.01) and the duration of action potential was extended ( < 0.05). The TASK-1 current was successfully inhibited by ML-365.</p><p><b>CONCLUSIONS</b>Diabetes can induce myocardial fibrosis and aggravate myocardial injury possibly in relation to changes in the protein expression and current of the two-port potassium channel TASK-1.</p>

Alteration of tetraethylammonium-sensitive potassium current in pulmonary artery smooth muscle cells of pulmonary hypertension rats / 中国药理学通报

Aim To investigate the alteration of volt-age-depending potassium channel(KV) current in pul-monary arterial smooth muscle cells(PASMCs) of pul-monary hypertension (PH) rats, and the effect of tet-raethylammonium (TEA,a blocker of KV) on potassi-um channel current in different PH models. Methods The whole-cell patch clamp techniques were applied to record the KVcurrents from PASMCs cultured with Ham's F-12 (1% FBS). Furthermore, the effects of TEA on the KVcurrents were examined in different PH models. Results The whole-cell KVcurrents were ob-viously inhibited in PASMCs of chronic hypoxia (CH)and monocrotaline (MCT)-treated rats. TEA signifi-cantly decreased the whole-cell KVcurrents in PASMCs of control and PH rats,and the inhibitory effect of TEA was dramatically reduced in PH group. Conclusions The degree of the voltage-dependent potassium chan-nels opening is significantly inhibited in PASMCs of CH and MCT-treated rats,accordingly,the TEA-sen-sitive KVcurrents obviously decrease.