Influence of Insulin on Plasma and Liver Vitamin A Levels in Diabetic Rats

It has been previously shown that plasma vitamin A concentration was decreased in both diabetic patients and streptozotocin diabetic rats. In the present study the effect of insulin administration to streptozotocin diabetic rats on plasma and liver vitamin A levels was determined. The daily insulin treatment began 3 weeks after the animals had been made diabetic and continued for 3 weeks. Plasma vitamin A levels were significantly lower in the diabetic rats than in the nondiabetic controls. In the insulin-treated diabetic rats, the plasma vitamin A together with the plasma glucose reverted to the control levels. Livers from the insulin-treated diabetic animals stored vitamin A in about the same amounts as did the livers of the untreated group but significantly more than those of the nondiabetic controls. The liver stores of vitamin A seem to reflect the amount of vitamin A consumed. These results demonstrate that treatment of diabetic rats with insulin restores plasma vitamin A to normal levels. However, the mechanism by which it does so remains to be determined.