Effects of Ischemin Preconditioning on Apoptotic Cell Death in Ischemia- Reperfused Rat Hearts

It was reported that apoptotic cell death was observed in ischemia-ｒeperfused rabbit heart as well as necrotic cell death. Ischemic preconditioning (PC) has a potent anti-myocardial infarction effect on the ischemia-reperfused model. However, the effects of PC on the apoptosis caused by the ischemia-reperfusion have never been clarified. We performed 30-min ischemia followed by 6-hour reperfusion with and without preceding 3 cycles of 5 minutes ischemia-reperfusion as PC in rats. Risk areas were determined by the injection of dye and infarct areas were defined by triphenyltetrazolium chloride atain. In situ terminal deoxynucleotidyl transferase (TdT) reaction and the electrophoresis of DNA were used for the detection of apoptosis. Hemodynamics showed no significant differences at any stages between control and PC groups. PC reduced infarct size from 25. 3% to 4.3% of the risk area (p < .01). PC reduced the number of TdT positive nuclei in the subendocardium, compared with control group (14.2±1.8 % vs 7.1±0.7 %, p < .01). Death of cardiomyocytes caused by ischemia-reperfusion in rats is not only attributed to necrosis but apoptosis, and PC significantly reduced both necrotic and apoptotic cell death especially in the subbendocardial area of the ischemic myocardium.