Response of extrapancreatic glucagon to glycemic changes under chronic insulin deficiency in dogs.

Abstract

Since the secretion of pancreatic glucagon is largely influenced by the changes in the blood glucose level, the response of extrapancreatic glucagon was investigated in totally pancreatectomized dogs under chronic insulin deficiency. Insulin-induced hypoglycemia did not alter plasma glucagon in the portal vein in a group of 5 pancreatectomized dogs, but the decrease of the blood glucose was small, by 70 mg/100 ml, in spite of a large amount of insulin. The administration of 2-deoxyglucose did not cause any changes in plasma glucagon in the portal vein in a group of 6 pancreatectomized dogs. Glucose-induced hyperglycemia, both transient and continuous, did not cause any changes in plasma glucagon in the portal vein, although blood glucose was significantly elevated. It is concluded that regulation of extrapancreatic glucagon differs from that of pancreatic glucagon.hypoglycemia ; hyperglycemia ; insulin ; glucose ; 2-deoxyglucose Since the establishment of radioimmunoassay for glucagon, a number of studies have been done concerning the regulation of the secreation of pancreatic glucagon. There have been, however, a few reports on the secretion of extrapancreatic glucagon, whose presence was demonstrated in 1974. The secretion of pancreatic glucagon is affected by changes in blood glucose (Ohneda et al. 1969), and glycemic changes are the most important among the various factors influencing the secretion of pancreatic glucagon. Therefore, we have studied the effect of glycemic changes upon the secretion of extrapancreatic glucagon in animals. Since there is no method to discriminate extrapancreatic glucagon from pancreatic glucagon (Srikant et al. 1977), the response of extrapancreatic glucagon has been investigated in totally pancreatectomized animals.We have already reported the response of extrapancreatic glucagon to glycemic changes immediately after pancreatectomy in dogs. However, different responses of extrapancreatic glucagon may possibly be evoked several days after pancreatectomy, because the circulating extrapancreatic glucagon increases about