Cardiac myofibrillar ATPase activity in diabetic rats

Diabetes was induced by an intravenous injection of 65 mg/kg streptozotocin and hearts were removed 8 weeks later for the isolation of myofibrils. The basal ATPase activity of myofibrils from diabetic hearts was significantly lower than the controls. Although Ca²⁺-stimulated ATPase activity was also depressed in diabetic myocardium, the dependency of diabetic myofibrils on free calcium concentration was not different from that of control. The basal and Ca²⁺-stimulated ATPase activities in diabetic rats demonstrated a greater sensitivity to KCl than control preparations. The myofibrillar basal ATPase, unlike Ca²⁺-stimulated ATPase, in diabetic animals exhibited a greater sensitivity to ethylene glycol. These results support the view regarding the presence of some subtle structural and conformational changes in diabetic myofibrils.