Effect of insulin on aldose reductase activity in the lens of rats with streptozotocin-induced diabetes

Sprague-Dawley rats (5 weeks old) were injected intravenously with 65mg of streptozotocin (STZ)/kg body weight. The diabetic rats were injected subcutaneously with insulin chronically or acutely and biochemical parameters in the lens were determined. Increases in aldose reductase (AR) activity and contents of sobitol, glucose and fructose were found in the STZ-diabetic rats, compared with normal control rats. When the STZ-diabetic rats were injected with 10 units of monotard insulin on each of 7 successive days, AR activity tended to decrease, and contents of sorbitol and fructose significantly decreased, but the glucose content did not significantly decrease, compared with STZ-diabetic rats given no insulin. There was no decrease in AR activity in the STZ-diabetic rats 3 hours after an injection of 10 units of actrapid insulin. These results demonstrated that the chronic administration of monotard insulin may decrease AR activity and sorbitol content in the lens of STZ-diabetic rats without lowering glucose levels.