Nitric oxide synthesis and the effect of aminoguanidine and NG-monomethyl-L-arginine on the onset of diabetes in the spontaneously diabetic BB rat

Abstract

Nitric oxide (NO) synthesis and the effect of aminoguanidine (AG) and NG-monomethyl-L-arginine (NMMA) (inhibitors of NO synthase) on the onset of diabetes were studied in the spontaneously diabetic BB rat. To measure in vivo NO production, 20 male 50-day-old diabetes-prone BB (BBdp) rats and age-matched non-diabetes-prone BB (BBn) rats were individually placed in metabolism cages. The animals had free access to a casein-based semipurified diet and deionized and double-distilled water. Urine excretion was collected every other day for 70 days, and urinary excretion of nitrate was measured as an index of in vivo NO synthesis. The urinary excretion of nitrate was enhanced by 150-200% in BBdp rats 4-6 days before the onset of diabetes, compared with aged-matched BBn rats. There was no difference in urinary excretion of nitrate between BBn rats and those BBdp rats that did not develop diabetes by the age of up to 120 days. To determine a role of NO in the development of spontaneous diabetes, 40-day-old male BBdp rats (30 rats per group) received daily subcutaneous injections of NMMA (acetate salt) (5 mg/kg body wt) or equal amounts of acetate (control) or oral administration of AG (0 or 3 g/l of drinking water) for 80 days. Both NMMA and AG delayed the onset of diabetes in BBdp rats by 13-15 days without altering the rate of incidence of diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)