Abstract： Objective To investigate the mechanism of protein kinase C(PKC) in immature myocardial ischemic preconditioning in order to further its clinical applicability. Methods Langendorff perfusion heart models of 24 rabbits were set up and they were randomly divided into 4 groups: ischemic reperfusion group (I/R group), myocardial ischemic preconditioning group (MIP group), chelerythrine group (CLT group) and protein kinase C group (PKC group). The emodynamics, biochemistry and myocardial ultrastructure were observed. Results The heart function recovery and myocardial water content in the MIP and the PKC groups were better than those of the I/R and the CLT groups (Plt;0.01). The adenosine triphosphate (ATP) content, superoxide dismutase activity, mitochondrial Ca2+-ATPase activity and synthesizing ATP activity of mitochondria in the MIP and the PKC groups were significantly higher than those of the I/R and the CLT groups (Plt;0.01). The dehydrogenase and creatine kinase leakage, malondialdehyde content, myocardial cell Ca2+ content and mitochondrial Ca2+ content in the MIP and the PKC groups were significantly lower than those of the I/R and the CLT groups (Plt;0.01). The myocardial ultrastructure injuries in the MIP and the PKC groups were less than that of the I/R and the CLT groups. Conclusion Myocardial ischemic preconditioning plays an important role in protecting immature myocardium, which is probably realized by the activation of PKC.
Objective To investigate the role of mitochondrial adenosine triphosphatesensitive potassium channel(mitoKATP) in immature myocardial ischemic preconditioning, and to provide evidence for immature myocardial protection. Methods Langendorff isolated heart infused model was used in the experiment. Twentyfour rabbits (aged from 14 to 21 days) were randomly divided into 4 groups：ischemiareperfusion group（I/R group）, myocardial ischemic preconditioning group(E1 group), 5hydroxydecanoate(5-HD) group (E2 group) and Diazoxide (Diaz) group(E3 group). Hemodynamics recovery rate, myocardial water content(MWC), the leakage rates of serum creatine kinase and lactate dehydrogenase, adenosine triphosphate content, superoxide dismutase activity, malondialdehyde content, myocardial cell Ca2+ content and myocardial mitochondrial Ca2+ content, myocardial mitochondrial Ca2+-ATPase activity, the adenosine triphosphate(ATP) synthesizing ability of myocardial mitochondria were tested, and myocardial ultrastructure was observed via electron microscopy. Results The hemodynamics recovery rate, myocardial water content(P＜0.05), adenosine triphosphate content, superoxide dismutase activity, myocardial mitochondrial Ca2+-adenosine triphosphyatase(ATPase) activity and the ATP synthesizing ability of myocardial mitochondria of the rabbits in E1 and E3 group were significantly better than that in I/R group and E2 group(P＜0.05). Malondialdehyde content, the leakage rates of serum creatine kinase and lactate dehydrogenase, myocardial cell Ca2+ content and myocardial mitochondrial Ca2+ content of the rabbits in E1 group and E3 group were significantly lower than that in I/R group and E2 group (P＜0.05). The myocardial ultrastructure injury in E1 and E3 group were significantly reduced compared with that in I/R and E2 group. Conclusion Myocardial ischemic preconditioning has significant protective effects on immature myocardium. Its mechanism may be related to the activation of mitoKATP.
Objective To investigate the immature myocardial protection effects with renal ischemic preconditioning. Methods 18 neonatal rabbits were randomly divided into three groups. Ischemic/reperfusion(I/R) group underwent 45 min ischemia followed with 45 min reperfusion after Langendorff model performed. Cardiac ischemic preconditioning(CIP) group underwent 45 min ischemia followed with 45 min reperfusion after 5 min ischemia and then 5 min reperfusion for two times. Renal ischemic preconditioning(RIP) group underwent 45 min ischemia followed with 45 min reperfusion after renal artery obstruction for 5 min and 5 min reperfusion for three times.The left ventricular function recovery,myocardial water content(MWC), lactate dehydrogenase (LDH) and creatine kinase(CK) leakage, malondialdehyde(MDA) content,adenosine triphosphate(ATP) content, superoxide dismutase(SOD) activity, myocardial cell Ca2+ ［Ca2+］c content,mitochondrial Ca 2+ content ［Ca2+］m,synthesizing ATP activity of mitochondria ［ATP］m and Ca2+ATPase activity of mitochondria ［Ca2+ATPase］m were tested. Results The recovery of postischemic heart function in RIP group and CIP group were higher than that I/R group(Plt;0.01). There were no significant difference of HR, AF in three groups （Pgt;0.05）. There were significant difference of CF，CO，LVSP and LVEDP in RIP group and CIP group than those I/R group（Plt;0.01）. There were significant difference of MWC, CK, LDH, ATP content, MDA, SOD activity, ［Ca2+］c content, ［Ca2+ATPase］m， ［Ca2+］m and ［ATP］m in RIP group than those I/R group（Plt;0.01). There were no significant difference between RIP group and CIP group upon every index (Pgt;0.05). Conclusion RIP has the same cardioprotection to immature myocardium as ischemic preconditioning.