CARDIOPROTECTIVE EFFECT OF D-PROPRANOLOL IN ISCHEMIC-REPERFUSED ISOLATED RAT HEARTS

In the isolated, perfused working rat heart, ischemia (15 min) decreas ed mechanical function and also the tissue levels of ATP and creatine phosphate, and increased the tissue levels of lactate and free fatty a cids including arachidonic acid. Reperfusion (20 min) did not restore mechanical function, but restored changes of metabolites incompletely except for free fatty acids, which changed further during reperfusion. Drugs were given 5 min before ischemia until the end of ischemia or f or the first 10 min after reperfusion. Both dl- and d-propranolol (10 and 30 muM) decreased mechanical function, accelerated the recovery of mechanical function during reperfusion following ischemia, and attenu ated ischemia reperfusion-induced metabolic changes. The attenuation o f reperfusion-induced metabolic changes was more marked when these dru gs were present during reperfusion. d-Propranolol showed a cardioprote ction similar to that by dl-propranolol. Timolol (50 muM) did not acce lerate the recovery of mechanical function during reperfusion, and did not attenuate the reperfusion-induced metabolic changes. These result s suggest that d-propranolol, like dl-propranolol, has a cardioprotect ive effect which is probably due to its membrane stabilizing (or sodiu m channel blocking) action.