Performance of diabetic rat hearts: effects of anoxia and increased work

An isolated perfused working rat heart preparation was used to assess the effect of alloxan-induced diabetes on myocardial performance. Ventricular performance was assessed under different aortic afterload, isoproterenol-stimulated and anoxic conditions. Basal left ventricular pressure development and rate of rise of ventricular pressure were depressed in hearts from diabetic animals. Neither coronary flow nor cardiac output were affected by diabetes. The dose and temporal responses to an infusion of isoproterenol were unaltered in diabetic hearts. Isoproterenol increased coronary flow by 50% and elevated ventricular pressure, dP/dt, and cardiac output by two- to threefold. Anoxia depressed ventricular pressure to below 20% of control within 5 min in both diabetic and normal hearts. Reoxygenation after 10 min of anoxia produced equivalent recovery in both groups working against a 52-mmHg aortic afterload, whereas recovery after 20 or 30 min of anoxia, was depressed in diabetic hearts. Elevating aortic afterload decreased performance of diabetic hearts and decreased their ability to recover from a 10-min anoxic exposure. Many of these observed differences in mechanical performance of diabetic hearts can be overcome by high glucose or insulin in the perfusion media.