Effects of Digestive Secretagogues on the Endocrine Pancreas in Man

Abstract

The rate of disposal of glucose administered to normal man by way of the gastrointestinal tract is greater than that of glucose given intravenously (1, 2, 3). This phenomenon is associated with potentiation of the increase in blood insulin in response to a rise in blood glucose concentration (4, 5). It has also been shown that ingestion of glucose or infusion of glucose into the duodenum in man provokes a rise in plasma glucagon-like immunoreactivity (GLI), whereas intravenous infusion of glucose results in no change or a fall in this activity (6, 7). The effect of alimentary glucose on glucose disposal (3) and blood insulin (8) are not impaired by portacaval anastomosis with ligation of the portal vein. Peripheral hyperglycaemia produced by infusions of glucose into peripheral or portal veins has been found to have equivalent effects on blood immunoreactive insulin (IRI) and GLI in man (9). It therefore appears that features distinguishing the response to ingested glucose from that to glucose administered intravenously, are not related to portal hyperglycaemia and probably depend upon alimentary function. These findings have revived the question of the possible role of humoral agents derived from the intestine in the regulation of the endocrine function of the pancreas, a problem that was the subject of extensive but inconclusive investigation in the past (10).