In order to investigate a possible short feedback mechanism of insulin secretion, the effect of prior infusion of bonito insulin upon glucose-induced insulin secretion in man was studied. The increase in plasma insulin after intravenous injection of a glucose solution was analysed under prior sustaining infusion of bonito insulin at the concentration of 12mU/0.5ml/min and 6mU/0.5ml/min. These concentrations of bonito insulin were shown to have had no effect on the blood sugar levels, nor on the basal insulin levels. After the prior eight hour infusion of exogenous insulin, the increase in glucoseinduced insulin secretion was significantly smaller than that produced after infusion of saline as a control. The magnitude of the inhibition in plasma insulin elevation was more remarkable at the higher dose of insulin. The level of blood sugar after glucose injection shown no significant change.
The half-life of immunoreactive insulin in plasma was determined after prior infusion of bonito insulin or saline for three hours. There was not tendency to any difference in T 1/2 between saline treated subjects and subjects who had received the rapid injection of porcine insulin prior to the infusion of bonito insulin.