Insulin has no effect on vascular endothelial growth factor expression in the retina of streptozotocin-induced diabetic rats

Abstract

Objective To investigate if insulin can affect the expression of vascular endothelial growth factor (VEGF) in the retina of streptozotocin-induced diabetic rats. Methods A total of 60 male Sprague-Dawley rats were randomly divided into sodium citrate buffer control group (CIT-CON, n= 30) and STZ-induced diabetic group (STZ-DM, n=30). At the 16th week, 24 rats from CIT-CON group at random were randomly divided to group A (sodium citrate buffer control group, n = 12) and group B (sodium citrate buffer plus insulin group, n= 12). The remaining 6 rats from as CIT-CON group served as negative control. At the same time, 24 rats from STZ-DM group at random were randomly divided to group C (STZ-induced diabetic group, n= 12) and group D (STZ-induced diabetic plus insulin group, n= 12). The remaining 6 rats from STZ-DM group also served as negative control. 4 IU of insulin was injected subcutaneously to rats of group B and D. Immunohistochemistry, Western blot and Real-time polymerase chain reaction (RT-PCR) were used to measure the expression level of VEGF protein and mRNA respectively. RESULTS Insulin significantly increased the VEGF mRNA (7.71 ± 0.25 vs 5.36 ±0. 37, t test P 0. 05) and protein expression (0. 5152±0. 0109 vs 0. 5099±0. 0100, t test P>0.05). Conclusions Insulin had no effect on VEGF expression in the retina of STZ-DM rats. Key words: Insulin/ physiology, Diabetic retinopathy/ etiology; Vascular endothelial growth factors / analysis; Disease models, animal