Oxidative protein damage parameters in plasma in chronic experimental diabetes in rats.

An increase in oxidative stress may contribute to the development of oxidative protein damage (OPD) in the streptozotocin-diabetic rat. To show the effect of hyperglycemia in promoting OPD, we determined protein carbonyl (PCO), nitrotyrosine (NT), total thiol (T-SH) and advanced oxidation protein product (AOPP) levels as markers of OPD, and lipid hydroperoxide (LHP) levels as a marker of lipid peroxidation in plasma of acute and chronic diabetic male Sprague-Dawley rats and their controls. The levels of the studied markers, except NT, were determined by colorimetric methods. NT levels were measured by ELISA. Plasma PCO and AOPP levels of chronic diabetic rats were increased significantly compared with those of both acute diabetic rats and the controls. Plasma NT levels of the three groups were not different. Plasma T-SH levels of acute diabetics were increased significantly compared with those of the controls while T-SH increase in the chronic diabetics was not significant. Plasma LHP levels were increased significantly in the chronic diabetic rats compared with those of the controls. The increase in plasma PCO, AOPP, LHP levels in chronic but not in acute diabetic rats may be indicating that persistence of hyperglycemia is involved in the evolution of OPD while plasma NT levels do not seem to reflect OPD in diabetes.