Abstract
Summary
The effect of iv glucagon on insulin release, as measured by immunoreactive insulin (IRI); and blood glucose (BG) concentration, was studied in beagle dogs. The dogs were used in the fasting state and during a constant iv infusion of a 50% glucose solution for three hours. BG and IRI were monitored during the infusion and one hour after the infusion was stopped. Intravenous glucagon (40 μg/kg) was administered during the sustained hyperglycemia and it elicited a further rise in IRI. At the same time, glucagon appeared to delay the disappearance rate of glucose from the blood. After the glucose infusion had been stopped, the injection of glucagon had a smal'ler effect on the plasma IRI. Glucagon injected into fasting animals failed to produce an IRI increase of the magnitude of that seen during hyperglycemia. It did, however, produce some increase in insulin output despite the initial relative hypoglycemic state of the fasting animal. Our data extends the work of others in suggesting that both BG levels and glucagon act together to produce a maximal beta cell response to conditions of caloric plethora.
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