EFFECT OF NUTRITIONAL STATE ON SUBSTRATE METABOLISM AND CONTRACTILE FUNCTION IN POSTISCHEMIC RAT MYOCARDIUM

The pattern of substrate utilization may influence postischemic myocar dial injury. To characterize the effect of nutritional state on substr ate selection and contractile function during control conditions and p ostischemic reperfusion, hearts from fed and fasted rats were perfused retrogradely with 0.4 mM palmitate, 8 mM glucose, and 175 mU/l insuli n. Under control conditions, hearts from fasted rats exhibited lower g lucose oxidation (-59%) and higher palmitate oxidation (+191%) than he arts from fed rats. During reperfusion, postischemic hearts exhibited stimulation of glucose oxidation, with no difference between hearts fr om fasted and fed rats. However, oxidation of palmitate remained highe r after fasting (+68%). Hearts from fasted rats exhibited lower left v entricular diastolic pressure and higher left ventricular systolic pre ssure development during reperfusion. The results indicate that 1) sub strate selection in myocardium is influenced by the nutritional state independently of substrate at availability, 2) during postischemic rep erfusion, inhibition of glucose oxidation is removed in hearts from fa sted rats, whereas inhibition of fatty acid oxidation in hearts from f ed rats is maintained, and 3) myocardial injury is lower after fasting .