The secretion of endogenous insulin was investigated through the effect of the infused exogenous bonito insulin on dogs. The systemic infusion of small doses of exogenous bonito insulin (0.3mu/kg) which proved inert on the blood sugar levels, resulted in an inhibition of endogenous insulin secretion. The prolonged infusion of exogenous bonito insulin inhibited both the basal insulin secretion and the biphasic pattern in glucose-induced insulin release. The mean level of endogenous insulin in the pancreatic vein decreased significantly (p<0.05) from 453±97μU/ml (immediately before the sustained infusion of exogenous bonito insulin) to 184±63μU/ml four hours after the start of the infusion. The calculated endogenous insulin output in the group treated with exogenous insulin also decreased significantly (p<0.05).
The two phases of glucose-induced insulin secretions in the insulin treated subjects were less marked than those in the control group (p<0.05), and occurred much more rapidly than those in the control.
These results suggest that the insulin secretion from the pancreas is affected by the prolonged infusion of exogenous bonito insulin.