Pancreatic and hepatic glycogen content in normoglycemic and hyperglycemic rats

As judged from morphological criteria, glycogen accumulates to a larger extent in insulin-producing B-cells than in acinar cells of the pancreas in situations of sustained hyperglycemia. In the present study, the glycogen content of the pancreatic gland and liver was measured in either euglycemic or glucose-infused hyperglycemic control rats, as well as in streptozotocin-induced diabetic rats. Whilst the glycogen content of the pancreas was significantly 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 STZ rats. From these measurements, it was estimated that, relative to wet weight, the glycogen content was, under the present experimental conditions, about 75 times higher in insulin-producing than other pancreatic cells. Moreover, it is proposed that the intravenous administration of glucagon may help in distinguishing between the glycogen present in the endocrine and exocrine moieties of the pancreatic gland, this hormone being apparently unable to provoke glycogenolysis in the exocrine pancreas, at variance with the situation prevailing in isolated pancreatic islets.