Objectives To investigate the effect of Gαq/11 signaling pathway and ATP-sensitive potassium channel ( KATP channel ) on ischemic preconditioning (IPC) protection in rat hearts. Methods Two series of experiments were...Objectives To investigate the effect of Gαq/11 signaling pathway and ATP-sensitive potassium channel ( KATP channel ) on ischemic preconditioning (IPC) protection in rat hearts. Methods Two series of experiments were performed in Wistar rat hearts. In the first series of experiment, ischemic preconditioning was induced by left anterior descending occlusion (three, 5 min episodes separated by 5 min of reperfusion), ischemia-reperfusion injury was induced by 30 min coronary artery occlusion followed by 90 min reperfusion. Hemodynamics, infarct size and scores of ventricular arrhythmias were measured. The expression of Gαq/11 protein in the heart was measured by Western blot analysis in the second series. Results Ischemic preconditioning rats showed decreased infarct size and scores of ventricular arrhythmia vs non-IP control rats. The effect of IPC was significantly attenuated by glibenclamide (1 mg/kg, ip), a nonselective KATP channel inhibitor. IPC caused a significant increase in the expression of Gαq/11 protein. Conclusions Activations of Gαq/11 signal pathway and KATP channel played significant roles in the classical cardioprotection of ischemic precon-ditioning rat heart and might be an important mechanism of signal transduction pathway during the ischemic preconditioning.展开更多
The myocardial protection afforded by ischernic preconditioning （IPC） can alleviate ischemi- a-repel-fusion injury in normal rat heart. However, this myocardial protection is seldom studied in the type 2 diabetic ra...The myocardial protection afforded by ischernic preconditioning （IPC） can alleviate ischemi- a-repel-fusion injury in normal rat heart. However, this myocardial protection is seldom studied in the type 2 diabetic rat with myocardial ischemia disease. In this study, we aimed to evaluate the effects of ATP-sensitive potassium channels （KATP channels） on IPC in the isolated type 2 diabetic rat heart and the role of the sul- fonylurea gliclazide. Methods Streptozotocin（STZ）-induced type 2 diabetic male Wistar rats with or without gliclazide （64 mg/kg body weight, orally） and age-matched non-diabetic control rats were used for all studies. The isolated hearts were perfused with Langendorff＇s system under the constant flow, pressure and tempera- ture conditions with Kreb＇s-Henseleit solution （K-H）. After 5 minutes of balance peffusion, these rats were randomly divided into six groups： non-diabetic control rats without IPC （CIR） ; non-diabetic control rats with IPC （CIP）; diabetic rats without 1PC （DIR）; diabetic rats with IPC （DIP）; gliclazide-treated diabetic rats without IPC （GIR）; and gliclazide-treated diabetic rats with IPC （GIP）. Groups CIR, DIR, and GIR were subjected to 30-rain global ischemia and 60-rain reperfusion for induction of ischemia/reperfusion injury. Groups CIP, DIP, and GIP were given three cycles of 5-min ischemia and 5-rain reperfusion as IPC, and then ischemia/reperfusion injury program was implemented. Extent of ischemia/reperfusion injury was measured in terms of the release of lactate dehydrogenase （LDH）, creatine kinase （CK）, and creatin kinase-MB （CK- MB） in coronary effluent. After perfusion, Kir6.2 and SUR2A mRNA expressions in the myocardial tissue were characterized by fluorescent quantitative real-time PCR method, and Kir6.2 and SUR2A protein expres- sions were assessed by immunohistochemistry. Result In non-diabetic control rats, the release of LDH, CK, and CK-MB in coronary effluent markedly decreased with IPC compared with No-IPC （P 〈 0.05）, but not in diabetic rats. However, in gliclazide-treated diabetic rats, IPC-induced decrease in the release of LDH, CK, and CK-MB was restored compared with No-IPC （P 〈 0.05）. The expressions of Kir6.2 both at mRNA and protein levels in CIP were significantly higher than those in CIR. There was no significant difference in theexpression of Kir6.2 and SUR2A both at mRNA and protein levels between DIP and DIR. However, the expression of Kir6.2 both at mRNA and protein levels was significantly higher in GIP than in GIR. No significant difference was detected in the mRNA expression level of SUR2A between the six groups. The expression of SUR2A at protein level was significantly higher in CIP than in CIR and in GIP than in GIR. Conclusions The cardioprotective effect of IPC is abolished in the isolated type 2 diabetic rats compared with non-diabetic control rats. However, to some extent, gliclazide can improve the myocardial protection of IPC against ischemia/reperfusion injury, thus suggesting that it is mediated mainly by KATP channels at mRNA or protein level, which provides a basis for further investigating the effects of KATP channels on IPC.展开更多
文摘Objectives To investigate the effect of Gαq/11 signaling pathway and ATP-sensitive potassium channel ( KATP channel ) on ischemic preconditioning (IPC) protection in rat hearts. Methods Two series of experiments were performed in Wistar rat hearts. In the first series of experiment, ischemic preconditioning was induced by left anterior descending occlusion (three, 5 min episodes separated by 5 min of reperfusion), ischemia-reperfusion injury was induced by 30 min coronary artery occlusion followed by 90 min reperfusion. Hemodynamics, infarct size and scores of ventricular arrhythmias were measured. The expression of Gαq/11 protein in the heart was measured by Western blot analysis in the second series. Results Ischemic preconditioning rats showed decreased infarct size and scores of ventricular arrhythmia vs non-IP control rats. The effect of IPC was significantly attenuated by glibenclamide (1 mg/kg, ip), a nonselective KATP channel inhibitor. IPC caused a significant increase in the expression of Gαq/11 protein. Conclusions Activations of Gαq/11 signal pathway and KATP channel played significant roles in the classical cardioprotection of ischemic precon-ditioning rat heart and might be an important mechanism of signal transduction pathway during the ischemic preconditioning.
基金supported by the Qingdao Municipal Science and Technology Commission (No. 11-2-3-2-(12)-nsh)
文摘The myocardial protection afforded by ischernic preconditioning （IPC） can alleviate ischemi- a-repel-fusion injury in normal rat heart. However, this myocardial protection is seldom studied in the type 2 diabetic rat with myocardial ischemia disease. In this study, we aimed to evaluate the effects of ATP-sensitive potassium channels （KATP channels） on IPC in the isolated type 2 diabetic rat heart and the role of the sul- fonylurea gliclazide. Methods Streptozotocin（STZ）-induced type 2 diabetic male Wistar rats with or without gliclazide （64 mg/kg body weight, orally） and age-matched non-diabetic control rats were used for all studies. The isolated hearts were perfused with Langendorff＇s system under the constant flow, pressure and tempera- ture conditions with Kreb＇s-Henseleit solution （K-H）. After 5 minutes of balance peffusion, these rats were randomly divided into six groups： non-diabetic control rats without IPC （CIR） ; non-diabetic control rats with IPC （CIP）; diabetic rats without 1PC （DIR）; diabetic rats with IPC （DIP）; gliclazide-treated diabetic rats without IPC （GIR）; and gliclazide-treated diabetic rats with IPC （GIP）. Groups CIR, DIR, and GIR were subjected to 30-rain global ischemia and 60-rain reperfusion for induction of ischemia/reperfusion injury. Groups CIP, DIP, and GIP were given three cycles of 5-min ischemia and 5-rain reperfusion as IPC, and then ischemia/reperfusion injury program was implemented. Extent of ischemia/reperfusion injury was measured in terms of the release of lactate dehydrogenase （LDH）, creatine kinase （CK）, and creatin kinase-MB （CK- MB） in coronary effluent. After perfusion, Kir6.2 and SUR2A mRNA expressions in the myocardial tissue were characterized by fluorescent quantitative real-time PCR method, and Kir6.2 and SUR2A protein expres- sions were assessed by immunohistochemistry. Result In non-diabetic control rats, the release of LDH, CK, and CK-MB in coronary effluent markedly decreased with IPC compared with No-IPC （P 〈 0.05）, but not in diabetic rats. However, in gliclazide-treated diabetic rats, IPC-induced decrease in the release of LDH, CK, and CK-MB was restored compared with No-IPC （P 〈 0.05）. The expressions of Kir6.2 both at mRNA and protein levels in CIP were significantly higher than those in CIR. There was no significant difference in theexpression of Kir6.2 and SUR2A both at mRNA and protein levels between DIP and DIR. However, the expression of Kir6.2 both at mRNA and protein levels was significantly higher in GIP than in GIR. No significant difference was detected in the mRNA expression level of SUR2A between the six groups. The expression of SUR2A at protein level was significantly higher in CIP than in CIR and in GIP than in GIR. Conclusions The cardioprotective effect of IPC is abolished in the isolated type 2 diabetic rats compared with non-diabetic control rats. However, to some extent, gliclazide can improve the myocardial protection of IPC against ischemia/reperfusion injury, thus suggesting that it is mediated mainly by KATP channels at mRNA or protein level, which provides a basis for further investigating the effects of KATP channels on IPC.
