Effects of hypothermia on the repolarization duration of ventricular myocytes in rats and its mechanism / 中国应用生理学杂志

To observe the effects of hypothermia on the repolarization duration and the expression of Kir2.1 protein of ventricular myocytes in isolated rat heart and explore the role of Kir2.1 protein. Eighteen healthy adult male Sprague-Dawley rats were randomly divided into three groups (n=6 per group): Control group (C group), 35℃ group (H group), 32℃ group (H group). Langendorff isolated heart models were established. After 15 min 37℃ K-H fluid banlanced perfusion, C group continued to perfuse the K-H solution at 37℃ for 30 minutes, H group continued to perfuse the K-H solution at 35℃ for 30 minutes, H group continued to perfuse the K-H solution at 32℃ for 30 minutes. At 15 min of balanced perfusion (T), and 30 min of continuous perfusion (T), the heart rate,and the MAP in the three layers of the left ventricular anterior wall were recorded, the action potential duration at 50% repolarization (MAPD), the action potential duration at 90% repolarization (MAPD) and transmural dispersion of repolarization(TDR) were calculated. At the same time, the occurrence of arrhythmia was recorded. The expression of Kir2.1 protein was measured by Western blot. The average optical density (AOD) and the distribution of Kir2.1 protein were measured by immunohistochemistry in the ventricular tissue measured by electrophysiology. Compared with T, the heart rate was decreased, MAPD and MAPD were prolonged significantly (P＜0.05), and TDR was increased significantly (P＜0.05) in H group, H group at T. Compared with C group, the HR was decreased, the MAPD was prolonged significantly (P＜0.05), TDR was increased significantly (P＜0.05),the expression and the AOD of Kir2.1 protein were decreased significantly (P＜0.05) in Hgroup, Hgroup at T. Compared with H group, the heart rate of H group was decreased significantly (P＜0.05), MAPD and MAPD were prolonged significantly (P＜0.05), and TDR was increased significantly (P＜0.05) at T. The distribution of Kir2.1 protein in group C was normal, while the distribution of Kir2.1 in H group and H group was disordered. Hypothermia prolonged the ventricular duration of repolarization and increased the dispersion of repolarization. The mechanism is related to the down-regulation the expression of Kir2.1 protein and the disorder of the distribution of Kir2.1 protein.

Kir2.1 Channel Regulation of Glycinergic Transmission Selectively Contributes to Dynamic Mechanical Allodynia in a Mouse Model of Spared Nerve Injury / 神经科学通报·英文版

Neuropathic pain is a chronic debilitating symptom characterized by spontaneous pain and mechanical allodynia. It occurs in distinct forms, including brush-evoked dynamic and filament-evoked punctate mechanical allodynia. Potassium channel 2.1 (Kir2.1), which exhibits strong inward rectification, is and regulates the activity of lamina I projection neurons. However, the relationship between Kir2.1 channels and mechanical allodynia is still unclear. In this study, we first found that pretreatment with ML133, a selective Kir2.1 inhibitor, by intrathecal administration, preferentially inhibited dynamic, but not punctate, allodynia in mice with spared nerve injury (SNI). Intrathecal injection of low doses of strychnine, a glycine receptor inhibitor, selectively induced dynamic, but not punctate allodynia, not only in naïve but also in ML133-pretreated mice. In contrast, bicuculline, a GABA receptor antagonist, induced only punctate, but not dynamic, allodynia. These results indicated the involvement of glycinergic transmission in the development of dynamic allodynia. We further found that SNI significantly suppressed the frequency, but not the amplitude, of the glycinergic spontaneous inhibitory postsynaptic currents (gly-sIPSCs) in neurons on the lamina II-III border of the spinal dorsal horn, and pretreatment with ML133 prevented the SNI-induced gly-sIPSC reduction. Furthermore, 5 days after SNI, ML133, either by intrathecal administration or acute bath perfusion, and strychnine sensitively reversed the SNI-induced dynamic, but not punctate, allodynia and the gly-sIPSC reduction in lamina IIi neurons, respectively. In conclusion, our results suggest that blockade of Kir2.1 channels in the spinal dorsal horn selectively inhibits dynamic, but not punctate, mechanical allodynia by enhancing glycinergic inhibitory transmission.

Effects of hyperoside on the myocardical activities of ATPases and expressions of Cx43 and Kir2.1 in arrhythmia rats induced by ischemia-reperfusion / 中成药

AIM To investigate the effects of hyperoside,an anti-arrhythmic agent capable of reducing myocardial infarct size,on arrhythmic rats induced by ischemia-reperfusion (I/R) and the corresponding mechanism.METHODS Male SD rats were randomly assigned to sham operation group,model group and hyperoside group (50 mg/kg,n =15).The I/R model was reconstructed by the ligation of left anterior descending coronary artery for 30 min ischemia.Rats in the hyperoside group were injected with 50 mg/kg hyperoside intraperitoneally 10 min before ischemia.Heart rate,mean arterial pressure (MAP) and heart rate systolic blood pressure product (RPP) at time points of 10 min before ischemia (T0),30 min after ischemia (T1),30 min (T2),60 min (T3),120 min (T4) after reperfusion were recorded.ELISA method was used to determine serum CK-MB and cTnI,spectrophotometry to measure Na+-K+-ATPase and Ca2+-Mg2+-ATPase levels,HE staining to observe myocardial tissue changes,immunohistochemistry to investigate Cx43 protein,and Western blot to detect Kir2.1 protein expression.RESULTS At T1,T2,T3 and T4,the model group demonstrated significantly lower HR,MAP and RPP than those in the sham operation group (P ＜ 0.05),whereas the hyperoside group had higher HR,MAP and RPP than the model group.Both hyperoside group and the model group shared significantly higher arrhythmia score,levels of CK-MB and cTnI than the sham operation group (P ＜ 0.05) while their lower activities of Na +-K +-ATPase and Ca2+-Mg2+-ATPase,protein expressions of Cx43 and Kir2.1 than the sham operation group were noticed as well.But the hyperoside group displayed its lower arrhythmia score,levels of CK-MB and cTnI,and yet higher activities of Na +-K +-ATPase and Ca2 +-Mg2 +-ATPase,protein expressions of Cx43 and Kir2.1 than the model group (P ＜0.05).CONCLUSION Hyperoside in improving ventricular arrhythmia of I/R rats may contribute to the activity restoration of Na +-K +-ATPase and Ca2 +-Mg2 +-ATPase,and the up-regulation of Cx43 and Kir2.1 protein expressions.

Changes of Kir4.1 and TASK-1 expression in rat Müller cell induced by SCH442416 at an elevated hydrostatic pressure in vitro / 中华实验眼科杂志

Objective To evaluate the effect of adenosine receptor antagonist SCH442416 on the expression of Kir2.1,Kir4.1 and TASK-1 in rat Müller cell at an elevated hydrostatic pressure in vitro.Methods Thirty SPF Sprague Dawley rats were purchased from Shanghai Slack Laboratory Animals Ltd.Cultured Müller cells were divided into normal control group (n =6),40 mmHg/24 hours (1 mmHg =0.133 kPa) group (n =6) and adenosine + SCH442416 intervention group (n =6).Müller cells were treated with 40 mmHg pressure for 24 hours in 40 mmHg/24 hours group,and Müller cells were treated with 40 mmHg pressure for 24 hours + 10 μ mol/L adenosine + 100 nmol/L SCH442416 in adenosine + SCH442416 intervention group.The real-time PCR,Western blot,whole-cell patch-clamp recordings and immunohistochemistry were used to detect Kir2.1,Kir4.1 and TASK-1 expression and Müller cells Kir currents.The experimental procedures were in accordance with the National Institutes of Health (NIH) guidelines for the Care and Use of Laboratory,and follow the 3R principle.Results Western blot assay showed that,following 40 mmHg pressure cultured for 24 hours,the expression of Kir4.1 and TASK-1 protein in Müller cell were significantly decreased by 38.6％ and 52.6％ compared with the normal control group,with significant differences between the two groups (both at P =0.000);Kir2.1 protein expression decreased by 14.7％,with insignificant difference between the two groups (P =0.082).Kir4.1 and TASK protein expression in adenosine + SCH442416 intervention group was increased by 60.7％ and 61.4％ compared with the 40 mmHg/24 hours group,with significant differences between the two groups (both at P =0.000);Kir2.1 protein expression in adenosine + SCH442416 intervention group was increased by 8.8％ compared with the 40 mmHg/24 hours group,with insignificant difference between them (P =0.354).Real-time PCR assay showed that,following 40 mmHg pressure cultured for 24 hours,Kir2.1,Kir4.1 and TASK-1 mRNA expression in Müller cells were significantly decreased compared with the normal control group,with significant differences between the two groups (P =0.047,0.001,0.000);Kir4.1 and TASK-1 mRNA expression in Müller cells in the adenosine + SCH442416 intervention group was significantly increased compared with the 40 mmHg/24 hours group,with significant differences between the two groups (P =0.038,0.030);however,there is no significant change in Kir2.1 mRNA expression (P =0.612).Conclusions SCH442416 upregulates the expression of Kir4.1 and TASK-1 mRNA and protein,but weakly affects the expression of Kir2.1.

THE EFFECTS OF POLYAMINE ANALOGUES AND POLYAMINE TOXIN ON EXPRESSED KIR 2.1 CHANNEL / 药物分析学报

ObjectiveTo test what length is needed for polyamine binding both intrinsic gate and pore docking site to block the cloned strong inwardly rectifying channel (Kir2. 1 channel). Methods The effect of alkylamine analogues (DA 5, DA 8, DA 10 and DA 12) and the competitive interaction of polyamine toxin, philanthotoxin (PhTx), on expressed Kir 2. 1channel in Xenopus oocytes were examined by using giant excised inside-out patch-clamp technique. ResultsThe results showed that along with the increase of the length of DAs ,the value of Kd decreased and the high affinity binding increased gradually. However,PhTx had the strongest effect on interfering the DA10 binding between intrinsic gate and pore docking site and had a less effect on DA12. Conclusion DA10 may be the right length for polyamine to block the channel. And maybe there is a hydrophobic interaction between DA12 and C-terminal domain of this channel, which then stabilize the DA12 binding between these two points and decrease the effect of PhTx on DA12.