Expression Pattern of Neuronal and Inducible NOS Isoforms in Insulin-dependent Diabetic Retinas after Treatment of L-NAME and Aminoguanidine

Abstract

Abstract: : Purpose: To investigate the influence of neuronal and inducible nitric oxide synthase (nNOS and iNOS) isoforms in the neural retina to insulin-dependent diabetes, altered expression of the two NOS isoforms was analyzed quantitatively by comparing the level in normal retinas, non-treated diabetic retinas and diabetic retinas differentially treated with NOS inhibitors, nitro-L-arginine methyl ester (L-NAME) and aminoguanidine (AMG). Methods: Insulin-dependent diabetic was induced by streptozotocin in Sprague-Dawley rats. The animals above 300 mg/dl blood glucose level were classified as diabetes, and divided into 8 experimental groups. The first is 1, 4, 12 and 24 week diabetics. The second and the third were daily injected with L-NAME in a volume of 40 or 80 mg/kg body weight for 4 weeks from just after onset of diabetes. The fourth and the fifth were treated with 40 or 80 mg/kg body weight L-NAME daily for 4 weeks from 8 week diabetic. The remainders were supplied drinking water being added AMG in a volume of 0.5g/l for first 1 week, 4 and 12 weeks after onset of diabetes, and then cared up to 12 week diabetic. The expression pattern of nNOS and iNOS was Western blot analyzed. Results: nNOS and iNOS were increased in the diabetic retinas with time-dependent manner. The expression level of both proteins has reached a peak value at 12 week diabetic. The expression level of both nNOS and iNOS throughout the diabetic retinas was remarkably decreased only at 12 week diabetics treated with both 80 mg/kg dosage of L-NAME from 8 week diabetic and AMG up to 12 weeks. Conclusions: With these results, it might be suggested that neural retinal damage is exacerbated from 12 week diabetic by over-produced NO from up-regulated nNOS and iNOS due to a certain reason of an insulin-dependent diabetic injury.

Keywords: nitric oxide • apoptosis/cell death • diabetes