Contents and secretion of glucagon and insulin in rat pancreatic islets from the viewpoint of their localization in pancreas.

Regional difference in secretion of glucagon and insulin from the rat pancreatic islets and their contents in pancreatic tissue and islets were studied. The glucagon content in the normal rat pancreas was the highest at the splenic part followed in order by the gastric, choledochal and duodenal parts. The effect of alloxan on the glucagon content was stronger in the dorsal lobe (combined gastric and splenic parts) than in the ventral lobe (combined duodenal and choledochal parts), and more increase of glucagon was found. The size of pancreatic islets was similar between the dorsal and the ventral lobe. The glucagon content in the islets was significantly higher in the dorsal lobe than in the ventral lobe, but the insulin content in the islets was similar in both lobes. The release of insulin from cultured pancreatic islets from the dorsal lobe was similar to that from the ventral lobe, but the release of glucagon was significantly high from the cultured islets of the former in the presence of glucose or arginine compared with that from the latter. Also in isolated pancreatic islets the release of glucagon was significantly more marked in the islets from the dorsal lobe by arginine administration. These findings show that the islets from the dorsal lobe secrete and contain more glucagon than those from the ventral lobe in contrast to there being a similar amount of release of insulin between them.