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Objective To investigate whether diazoxide preconditioning can exert protective effect on myocardium against ischemia-reperfusion injury in immature rabbits and the possible mechanism. Methods Twenty-one healthy 3-4 week old white rabbits of either sex were randomly divided into 3 groups : group Ⅰ control ( n = 8) ; group Ⅱ diazoxide preconditioning ( n = 8) and group Ⅲ diazoxide + 5-HD preconditioning ( n = 5) . The animals were anesthetized with intraperitoneal pentobarbital 50 mg?kg-1 and heparized (150 IU?kg-1). The hearts were excised and connected to Langendorff apparatus and passively perfused with normothermic (37℃), oxygenated (95% O2 , 5% CO2) Krebs-Henseleit buffer (KHB) at a constant perfusion pressure of 70cmH2O. A latex balloon was inserted via left atrium into left ventricle and filled with water. The left ventricular end-diastolic pressure (LVEDP) was maintained at 10 mm Hg. In group I cardiac arrest was induced with St Thomas Ⅱ solution after the heart was perfused with KHB for 30 min. In group 11 after being perfused with KHB for 15 min, the hearts were perfused with diazoxide 100?mol?L-1 for 5 min followed by 10 min wash-out with KHB , then cardiac arrest was induced as in group Ⅰ . In group Ⅲ after being perfused with KHB for 15 min, the hearts were perfused with diazoxide 100?mol?L-1 and 5-HD 100?mol?L-1 for 5 min, followed by 10 min wash-out with KHB, then the cardiac arrest was induced as in group Ⅰ and Ⅱ . All hearts were subjected to 30 min ischemia followed by 45 min reperfusion after cardiac arrest. Coronary flow (CF), HR, left ventricular developed pressure (LVDP) and dp / dt max were measured after the hearts were perfused with KHB for 15 min (baseline) and at 5, 10, 15, 30, 45 min after reperfusion was resumed. Coronary effluent was collected at 5 min after reperfusion was resumed for determination of myocardial enzymes, CK, LDH and AST. At the end of experiment myocardial specimen was obtained for determination of ATP content and ultrastructure examination. Results There was no significant difference in the baseline hemodynamic parameters among the three groups. The rates of recovery of LVDP and ? dp / dt max after reperfusion were significantly higher in group Ⅱ than those in group I and Ⅲ ( P 0.05 ) , Conclusion Diazoxide can protect myocardium from ischemia-reperfusion injury by opening the mitochondrial KATP channel in immature rabbits.
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Objective To investigate the role of mitochondrial KATP channel in the mechanism of the protective effect of ischemic preconditioning (IP) against ischemia-reperfusion (I/R) injury.Methods Forty-eight Wistar rats of both sexs weighing 250-350 g were used in this study. Forty rats were randomly divided into 5 groups ( n = 8 each): group A I/R; group B IP+ I/R; group C diazoxide (DZ mito-KATP channel activator) + I/R; group D 5-HD (mito-KATP channel blocker) + IP + I/R and group E 5-HD + DZ + I/R. Another 8 animals were used for electron microscopic examination of normal mitochondria as control. The animals were anesthetized with intraperitoneal pentobarbital 30 mg?kg-1. The hearts were immediately excised and passively perfused in a Langendorff apparatus with K-H solution at 5.8 kPa perfusion pressure and 36.5-37.5℃ via aortic cannulation. A fluid-filled latex balloon was via left atrium in left ventricle for the measurement of left ventricular function. I/R was induced after 30 min stabilization by clamping aortic cannula for 40 min followed by 30 min reperfusion. In group B and D the isolated hearts underwent 2 episodes of 5 min ischemia followed by 5 min reperfusion before I/R. In group C and E DZ 50 ?mol?L-1 was infused for 10 min and in group D and E 5-HD 100 ?mol?L-1 was infused for 10 min before I/R. HR, LVSP, LVEDP and coronary flow (CF) were measured at the end of stabilization (T0 , baseline), immediately before I/R (T1 ) and at 10, 20 and 30 min of reperfusion (T2.3.4.), and left ventricular developed pressure (LVDP= LVSP- LVEDP) was calculated. Myocardial tissue was obtained at the end of 30 min reperfusion for electron microscopic examination of mitochondria. Mitochondrial ultrastructure was assessed by Flameng scoring system (0 = normal, 4 = severely damaged) .Results Ischemic and DZ preconditioning significantly increased LVDP and decreased LVEDP and Flameng score. 5-HD pretreatment partly antagonized the protective effect of IP and completely antagonized that of DZ against I/R injury. Conclusion Ischemic preconditioning protects the heart against I/R injury mainly by activating mitochondrial KATP channel.
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AIM: To investigate the protective effects and mechanisms of modified acidic fibroblast growth factor (maFGF) in anoxic reperfusion of rat hearts. METHODS: Using Langendorff apparatus, we established the model of anoxia/reperfusion of isolated hearts to compare the protective effects of maFGF and acidic fibroblast growth factor (aFGF). The changes of left ventricle development pressure (LVDP) and maximal rates of rise of ventricular pressure(dp/dt_~max ), maximal rates of decline of ventricular pressure (dp/dt_~min ) were determined, changes of LDH and MDA levels,SOD activity in efflux from coronary artery were also detected at different time point. RESULTS: Pretreatment with maFGF and aFGF produced a similar protective effect on myocardium during anoxia /reperfusion, including promoting obviously heart functional recovery after myocardial anoxia/reperfusion and reversing changes of LDH, MDA contents and SOD activity induced by anoxic/reperfusion. CONCLUSION: maFGF has a protective effect on anoxia/reperfusion heart, and the mechanism of this effect may be related to suppression of lipid peroxidation.