The role of nitric oxide in mediating pancreatic endocrine responses to insulin-induced hypoglycaemia in the conscious calf

The role of nitric oxide (NO) in mediating pancreatic endocrine responses t o moderate hypoglycaemia has been investigated in conscious unrestrained ca lves. The synthesis of endogenous NO was inhibited by the administration of N-nitro-L-arginine methyl eater (L-NaME; 100 mg kg(-1) I.A.), while sodium nitroprusside was infused continuously (2-4 mu g min(-1) kg(-1) I.V.) to m imic the tonic production of NO. This effectively abolished the rise in pla sma pancreatic polypeptide (PP) concentration during moderate hypoglycaemia (0.7 nmol kg(-1) insulin I.V.) and significantly reduced the response to m ore intense hypoglycaemia (2.0 nmol kg(-1) insulin I.V.). In contrast, the glucagon response was not significantly affected in either group, although consistently higher plasma glucagon values were obtained in response to the higher dose of insulin following the administration of L-NAME. It is concl uded that, in the absence of L-NAME, production of NO contributes to the PP response, but not the glucagon response to hypoglycaemia in this species u nder physiological conditions.