Pancreatic and hepatic glycogen content in normoglycemic and hyperglycemicrats

As judged from morphological criteria, glycogen accumulates to a larger ext ent in insulin-producing B-cells than in acinar cells of the pancreas in si tuations of sustained hyperglycemia. In the present study, the glycogen con tent of the pancreatic gland and liver was measured in either euglycemic or glucose-infused hyperglycemic control rats, as well as in streptozotocin-i nduced diabetic rats. Whilst the glycogen content of the pancreas was signi ficantly higher in STZ rats than in control euglycemic rats, it was further enhanced in glucose-infused control rats, despite the fact that the latter animals were not more severely hyperglycemic and for a shorter time than S TZ rats. From these measurements, it was estimated that, relative to wet we ight, the glycogen content was, under the present experimental conditions, about 75 times higher in insulin-producing than other pancreatic cells. Mor eover, it is proposed that the intravenous administration of glucagon may h elp in distinguishing between the glycogen present in the endocrine and exo crine moieties of the pancreatic gland, this hormone being apparently unabl e to provoke glycogenolysis in the exocrine pancreas, at variance with the situation prevailing in isolated pancreatic islets.