EXTRAPANCREATIC ISLETS OF LANGERHANS - ONTOGENY AND ALTERATIONS IN DIABETIC CONDITION

The existence of extrapancreatic islets in the duodenal mucosa of the adult rat has been established by morphological studies and the develo pment of these islets has been followed from the early embryonic stage to neonatal and adult life. Like the pancreatic islets, glucagon cell s were the first to appear at day 12 of gestation. However, in contras t to the pancreatic islets, insulin was not detected in the extrapancr eatic islets until birth. At this stage, the different endocrine cells assume their classical topography, insulin cells being surrounded by non-insulin endocrine cells. In addition, the behaviour of these extra pancreatic islets in diabetic conditions was evaluated on streptozotoc in-induced diabetic rats as well as on spontaneous BE Wistar diabetic rats. In both conditions, the extrapancreatic islets were found in the duodenal mucosa but were mainly composed of glucagon cells, the insul in cells having disappeared. These results demonstrate that the extrap ancreatic islets are a common normal feature of the rat duodenal mucos a. They appear during fetal development, are present in different stra ins of rats and behave similarly to the pancreatic islets under sponta neous or chemically induced diabetic conditions. Although their exact role remains to be established, they probably react to local hyperglyc aemic environment due to intestinal absorption.