Comparison of inducible nitric oxide synthase activity in pancreatic islets of young and aged rats

Objective(s):Some pathologic situations such as diabetes and metabolic syndrome are associated with alternation in nitric oxide level. Incidence of these condition increases with aging. On the other hand, insulin secretion is modulated by nitric oxide, and nitric oxide synthase (NOS) activity is also altered in diabetes. In this study, modification in the enzyme activity associated with aging and also optimized procedure for islet NOS assay was investigated. Materials and Methods: Male Wistar rats were randomly divided in two experimental groups: A: adult rats; were ۴ month old and B: old rats; were ۱۲ month old. In all groups, plasma glucose, insulin and NOX (nitrite + nitrate = NOX) were measured, and also insulin secretion in isolated pancreatic islet with or without L-NAME was investigated. Furthermore, the inducible NOS activity with L-citrulline measurement in islets was measured. Results: L-citrulline was quantified using one step HPLC column. Aging induced hyperglycemia (P<۰.۰۵) and excess plasma NOX (۱۷.۷۴ ± ۱.۶۶۴ and ۲۶.۲۵ ± ۲.۱۶۶ μmol/l in A and B groups respectively, P<۰.۰۵) with unaltered plasma insulin. Islet insulin secretion was significantly reduced in aging rats. L-NAME induced islet insulin secretion especially in aging rats (P=۰.۰۰۳). Inducible NOS activity in islets of aging rats was significantly higher than adult rats (۱.۰۸۲ ± ۰.۰۸۴ and ۶.۲۷۷ ± ۰.۴۷۵ pmol/min per mg protein in adult and aging rats, respectively, P<۰.۰۰۱). Conclusion: These findings show that decreased in islet insulin secretion may be related to increase in iNOS activity in islets, which follows impaired carbohydrate metabolism in aging.

کلیدواژه ها:

Aging ، High performance liquid chromato-graphy ، Islet ، L-citrulline ، Nitric oxide synthase activity ، Rat