Insulin and islet cell transplants: effects on diabetic rat cardiac myofibril ATPase.

Streptozotocin-induced diabetes results in depression of growth rate, cardiac myofibril ATPase activity, and elevated plasma glucose levels. Reversibility of these changes with daily insulin injections and pancreatic islet cell transplants was investigated and compared. Cardiac myofibril ATPase activities (mumol Pi X mg-1 X min-1) were depressed in the uncontrolled diabetic (D) group over the complete range of Ca2+ concentrations tested (e.g., 0.057 +/- 0.017 at 10 microM free Ca2+) with respect to the control (C) group (0.113 +/- 0.009). Neither the transplanted (T) group (0.128 +/- 0.017) nor the insulin injected (I) group (0.111 +/- 0.014) was significantly different from the C animals. Normal growth rates were restored in both I and T groups, whereas in the D group weight gains were negligible in comparison. Cardiac myofibril protein yields (in mg/g wet wt) were not significantly different among groups. These findings indicate that both islet cell transplants and daily insulin injections are capable of normalizing plasma glucose levels, cardiac myofibril ATPase activity, and growth rates in STZ-diabetic rats.