Pancreatic primordia from normal rat embryos of 14.5 to 15.5 days postcoitum were grown in organ culture on liquid media with 173, 350, 526 and 995 nig. of glucose per 100 ml. The periods of culture were as follows: eight days (14.5 day embryos) and six days (15.5 day embryos). In cultures grown on the standard medium with 173 mg. of glucose per 100 nil., the pancreatic islets had many granulated beta cells. In cultures grown on high-glucose media with 350, 526 and 995 mg. of glucose per 100 nil. the islets had fewer granulated beta cells.
These observations are interpreted to mean that highglucose levels in the media inhibit the production of granulated beta cells in the islets of the cultures.