ABSTRACT
A number of studies have provided evidence for the existence of gastrointestinal motilin in other species. The isolation of gastric inhibitory polypeptide (GIP) resulted from studies which demonstrated that crude preparations of cholecystokinin (CCK) contained gastric acid secretion inhibitor. The localization of GIP in the endocrine pancreas is controversial, yet it is important since if it were present it would imply an intra-islet function. Oral administration of fat is also a potent stimulant for GIP release. The acid inhibitory properties of porcine GIP, and the fact that it was released in response to fat, suggested that it could be a physiological enterogastrone. The major physiological role for GIP is probably as a component of the enteroinsular axis. At present there is no data indicating that GIP has a direct effect on gonadal steroid metabolism and only limited information suggesting that it can influence reproductive hormone secretion from the pituitary.
