The effect of sulpiride on the endocrine pancreas (author's transl)

Abstract

In order to clarify the possible participation of dopaminergic control on the endocrine pancreas, a dopaminergic antagonist, sulpiride, was given intravenously to 12 normal subjects and 26 diabetics. After the intravenous administration of sulpiride with or without arginine HCl, blood samples were withdrawn at 0, 15, 30, 45, 60, 90 and 120 min and were stored at -20°C until the measurements of blood glucose, serum immunoreactive insulin (IRI) and plasma immunoreactive glucagon (IRG) were taken.In the first experiment, 100mg of sulpiride was administered solely to 5 normal subjects and 7 diabetics. Though blood glucose levels were not significantly changed, plasma IRG levels were significantly lower at 45 min after the injection in normal subjects and at each 30, 60 min in diabetics. From the results of the first experiment, sulpiride was thought to be able to suppress plasma IRG levels; then the second experiment was performed.In the second experiment, 7 normal subjects and 19 diabetics were employed. Both arginine HCl infusion and arginine HCl with 100mg sulpiride infusion were performed in order to compare the difference between IRI and IRG responses to the two provocations. In comparison with the arginine HCl infusion, IRI secretion seemed to be enhanced and IRG secretion seemed to be diminished in the simultaneous administration of arginine HCl and sulpiride. This was more obvious in comparing a glucagon or insulin area which was calculated by the integration of the curves circumscribed by a plasma IRG or serum IRI for the periods of 0-120 min. The glucagon area was significantly (p <0.05 in normal subjects; p <0.01 in diabetics) smaller in arginine HCl and sulpiride infusion than in arginine HCl alone. The insulin area seemed to be greater with the simultaneous administration of arginine HCl and sulpiride than with arginine HCl alone, but this difference was not significant.It was found through the two experiments that the dopamine antagonist, sulpiride, suppressed the basal and arginine-induced IRG secretion. Therefore, the results of the present study might suggest the existence of a dopaminergic system in the endocrine pancreas.