Effect of insulin on the expression of intraocular vascular endothelial growth factor in diabetic rats

To investigate the long-term effect of insulin on vascular endothelial growth factor (VEGF) of streptozotocin (STZ)-induced diabetic rats.

Male Sprague-Dawley rats received intraperitoneal injections of STZ (60 mg/kg) to induce diabetes. The diabetic rats were divided into two groups: the poorly controlled diabetic group (4 U of Ultratard week) and the insulin-controlled group (2-8 U of Ultratard per day according to blood glucose level). The animals were sacrificed 4 months after diabetes induction. The intraocular fluids of four eyes from two rats were pooled together as one sample. VEGF was checked using an enzyme-linked immunosorbent assay (ELISA) kit.

There were eight rats in the poorly controlled diabetic group, 13 in the insulin-controlled group and 10 in the healthy group. The concentration of VEGF ranged from 70.72-164.89 pg/ml (mean, 99.60 +/- 31.37 pg/ml) in the poorly controlled diabetic group, 65.17-124.33 pg/ml (mean, 79.05 +/- 21.50 pg/ml) in the insulin-controlled group and 50.6-67.6 pg/ml (mean, 58.07 +/- 6.49 pg/ml) in the healthy group. There were statistical differences between groups (ANOVA, p < 0.001). The mean difference between the poorly controlled diabetic group and the insulin-controlled group was 20.55 +/- 9.61 pg/ml (p = 0.041).

The concentrations of VEGF in the two diabetic rat groups were higher than that in the healthy rat group. Insulin control reduced the rise of VEGF.