Abstract

BACKGROUND
Diabetes mellitus could occur when insulin secretion of pancreas is inadequate in response to blood glucose. The mechanisms on failure of pancreatic beta cell are still not known. Several recent experiments have reported that nitric oxide (NO) may be considered as a modulator of insulin secretion and impairment associated with the beta cell. The present study was purposed to investigate the role of nitric oxide on the secretion of insulin of rat pancreas in vivo and in vitro. METHODS: The plasma insulin and glucose were measured after intravenous injection of nitric oxide synthase (NOS) inhibitor (NG-nitro-L-arginine methyl. ester, L-NAME) in male rat. Insulin release was determmed during stimulation of NOS inhibitor and nitric oxide donor (hydroxylamine) in the isolated pancreatic islets. RESULT: 1. The insulin secretory response with L-arginine stimulation after injection of NOS inhibitor (L-NAME) in rat was increased resulting in mild hypoglycemia which recovered promptly. This showed that NO were related with L-arginine induced insulin secretion. 2. After isolation of pancreatic islet, 11,0 mM glucose induced insulin release was increased in culture media and L-arginine (1.0 mM) induced insulin release was also increased compared with control (6.72+/-0.66 vs. 3.48+/-0.42 prnol/islet/hour, p<0.05). 3. L-arginine induced insulin release was increased with L-NAME in the isolated rat pancreatic islets (12.5+/-1.38 vs, 7.23+/-0.93 ng/islet/ hour, p<0.05). 4. Glucose induced insulin release was progressively inhibited by NO donor hydroxylamine in the isolated rat pancreas islet (6.72+/-0.75 vs. 2.46+/-0.60 pmol/islet/hour p<0.05). CONCLUSION: These results strongly suggest that nitric oxide is a negative modulator of insulin release in normal rats induced by the nutrient secretagogues L-arginine and glucose in vivo and in vitro. Further investigation on the mechanism of nitric oxide in insulin secretory pathway will be necessary.

• Keywords: Nitric Oxide;insulin secretion;Rat pancreas;Islet culture