title: Comparison of inducible nitric oxide synthase activity in pancreatic islets of young and aged rats.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Male Wistar rats were randomly divided in two experimental groups: A: adult rats; were 4 month old and B: old rats; were 12 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<0.05) and excess plasma NOX (17.74 ± 1.664 and 26.25 ± 2.166 μmol/l in A and B groups respectively, P<0.05) with unaltered plasma insulin. Islet insulin secretion was significantly reduced in aging rats. L-NAME induced islet insulin secretion especially in aging rats (P=0.003). Inducible NOS activity in islets of aging rats was significantly higher than adult rats (1.082 ± 0.084 and 6.277 ± 0.475 pmol/min per mg protein in adult and aging rats, respectively, P<0.001).
  
  
  CONCLUSIONS
  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.
authors: Department of Physiology and Biophysics, Faculty of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran.
authors: Khadije
authors: K
authors: Farrokhfall
authors: Department of Marine Living Sciences, Iranian National Institute for Oceanography and Atmospheric Sciences (INIOAS), Tehran, Iran.
authors: Mehri Seyed
authors: MS
authors: Hashtroudi
authors: Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors: Asghar
authors: A
authors: Ghasemi
authors: Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran.
authors: Hossein
authors: H
authors: Mehrani
keywords: Aging; High performance liquid chromatography; Islet; L-Citrulline; Nitric oxide synthase activity; Rat