Abstract： Objective To investigate the effects of calcium preconditioning (CP) on immature myocardial cell apoptosis and apoptosisregulated proteins. Methods The experiment was carried out from June 2000 to December 2001 in the Renmin Hospital of Wuhan University. Twelve rabbits with the age of 1421 d and the weight of 230300 g were divided into 2 groups with 6 in each group by random digital table. For rabbits in the ischemia/reperfusion group (I/R group), after Langendorff models were routinely set up, KrebsHenseleit (KH) solution was perfused for 20 minutes and reperfused for 120 minutes after 45 minutes of ischemia. For rabbits in the CP group, after Langendorff models were established, KH solution was perfused for20 minutes, and 45 seconds’ noncalcium KH solution perfusion and 5 minutes’ KH solution perfusion were repeated 3 times before 45 minutes of ischemia and 120 minutes of reperfusion of KH solution. In situ apoptosis identification and semiquantitative analysis were used to detect the myocardial cell apoptosis; agarose gel electrophoresis was used to detect the nucleosomal ladder of DNA fragments; and the expression of bcl-2, bax and fas were detected with Western blot method. Results The apoptosis rate for the CP group was lower than that of the I/R group (4.53%±1.22% vs. 12.30%±2.12%,t=7.780, P=0.000). Nucleosomal ladder of DNA fragments of the CP group was lower than that of the I/R group (OD value: 56 460±1 640 vs. 135 212±3 370,t=51.460,P=0.000). The expression of bcl-2 in the I/R group was lower than that of the CP group (OD value: 13 217±1 770 vs. 31 790±1 018,t=22.280, P=0.000). The expression of bax (OD value: 30 176±1 025 vs. 7 954±730, t=43.260, P=0.000) and fas (OD value: 29 197±1 233 vs. 8 140±867, t=34.220, P=0.000) in the I/R group was higher than that of the CP group. Conclusion CP can affect the expression of myocardial bcl-2, bax, and fas, and decrease immature myocardial cell apoptosis.
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.