Forty pregnant rats were made diabetic by injecting alloxan intravenously on day 11.5 of pregnancy. On day 19.5 or day 21.5 the mothers were killed and their fetuses obtained for study. Pieces of fetal pancreases were grown in organ cultures on liquid media containing varying amounts of glucose for two to four days. At the time of the explantation, the beginning control pancreases contained virtually no granulated beta cells.
In cultures grown on the standard media (about 175 mg. of glucose per 100 ml.), the pancreatic islets had acquired many granulated beta cells. In those grown on the highglucose media (about 350, 500 and 1,000 mg. per 100 ml.) the islets had either few granulated beta cells or none. These observations complement our previous findings in pancreatic cultures from normal rat embryos.
The insulin content of the media after incubation was within the range of the insulin concentration in the blood of normal fed rats. The insulin content in the media after days 3-4 of culture was considerably greater than that after 1-2. The high-glucose levels in the media did not cause an increase in the insulin content of the media. Our studies suggest that the high-glucose levels in the media inhibited the synthesis (and/or storage) of insulin in the pancreatic culture.