Effect of insulin treatment on long-term diabetes-induced alteration of myocardial function.

Six months following the induction of diabetes by streptozotocin (50 mg/kg i.v.) diabetic rats exhibited elevated levels of plasma glucose and glycosylated hemoglobin. Plasma insulin levels were 50% of control and diabetic animals weighed significantly less than control. Using a working heart preparation it was found that (+) and (-) dP/dt and left ventricular pressure development (LVDP) was decreased in hearts from diabetic animals. Insulin treatment (9 U/kg/day s.c. of protamine zinc insulin) for 4 weeks prior to sacrifice restored body weight and plasma insulin to normal. Plasma glucose and glycosylated hemoglobin levels were significantly decreased towards normal in insulin treated diabetic rats. LVDP and (+) dP/dt was also partially returned to normal in insulin treated diabetic rats while (-) dP/dt was completely reversed to normal. Thus, 4 weeks of insulin treatment to rats previously diabetic for 5 months partially or totally reversed the changes produced by diabetes.