EFFECT OF MAGNESIUM ADMINISTERED DURING POSTISCHEMIC REPERFUSION ON MYOCARDIAL OXIDATIVE-METABOLISM IN ISOLATED RAT HEARTS

To determine the effect of magnesium on myocardial function and oxidat ive metabolism after reperfusion, isolated rat hearts perfused retrogr adely with erythrocyte-enriched medium (0.4 mM palmitate bound to 0.4 mM albumin, 11 mM glucose) were subjected to 60 minutes of no-flow isc hemia followed by 60 minutes of reperfusion. Untreated postischemic he arts exhibited after 15 minutes of reperfusion recovery of myocardial oxygen consumption to 65% of the preischemic value despite persistent depression of left ventricular isovolumic pressure development to 21%. Magnesium (15 mM) administered during the initial 30 minutes of reper fusion reduced myocardial oxygen consumption of reperfuse myocardium b y 35%. Oxidation of [1-C-14]palmitate was slightly more reduced (-55%) than oxidation of [U-C-14]glucose (-42%). Magnesium did not influence ultimate recovery of contractile function and cumulative myocardial r elease of creatine kinase. Thus, 15 mM magnesium administered during r eperfusion elicited a reduction of oxidative metabolism. However, magn esium did not modify myocardial injury.