Combination of Ischemic Preconditioning and Postconditioning in Isolated and Intact Rat Hearts: Does it Work or Not?

Abstract

Ischemic preconditioning (Pre) phenomenon was well known as cardioprotective effects and its signaling pathways leading to myocardial protection activated by NO/cGMP pathways. In the meantime, the ischemic postconditioning (Post) in which brief intermittent repetitive interruptions to reperfusion at the onset of timely reperfusion after a prolonged period of ischemia also reduced myocardial injury to an extent comparable to Pre. In isolated working heart experiment, all hearts were subjected to 30 min of regional ischemia and 120 min of reperfusion: Control, no intervention; Pre, 3 cycles of 5-min of global ischemia and 5 min of reperfusion before the ischemic insult, Post; 6 cycles of 10 sec of reperfusion followed by 10 sec of global ischemia immediately after the index ischemia; Both (Pre + Post). Infarct size, coronary flow (CF), heart rate (HR), left ventricular developed pressure (LVDP), and +dP/dt were measured. The infarct size in the Pre (n=7, 18.5% ± 2.1%), Post (n=7, 19.1% ± 1.5%), and Both (n=10, 21.7% ± 1.7%) groups was significantly decreased compared with Control (n=7, 29.9% ± 1.7%). However, there was no additive effect when Pre and Post were combined. There were no significant differences in baseline CF, HR, LVDP, +dP/dt among the groups, and no significant differences in HR, LVDP, +dP/dt in all groups after 2 hours of reperfusion. In conclusion, Pre and Post, Both group improved cardioprotective effects than Control group. However, combination of ischemic preconditioning and postconditioning showed no additive cardioprotective effects in isolated rat heart models.