Effect of Insulin Treatment upon Responsse of Extrapancreatic Glucagon to Arginine

抄録

In order to investigate the effect of insulin treatment upon the secretion of extrapancreatic glucagon, arginine infusion was performed in normal dogs and alloxan diabetic dogs with or without insulin treatment at conscious and anesthetized states. In a series of experiments with conscious dogs, alloxan diabetic dogs revealed not only elevated fasting levels of plasma glucagon but also exaggerated glucagon response to arginine. Insulin treatment in the alloxan dogs reduced the fasting plasma glucagon levels as well as responsiveness of glucagon to arginine. In the experi-ments with anesthetized dogs, plasma glucagon in the portal vein of the normal dogs rose only slightly in response to arginine infused after total pancreatectomy. In contrast, the alloxan diabetic dogs revealed an increase in plasma glucagon following arginine infusion performed after pancreatectomy. The response of plasma glucagon to arginine was reduced after pancreatectomy in the alloxan diabetic dogs with insulin treatment. Total immunoreactive glucagon (IRG) measured by a non-specific antiserum, increased in response to arginine after pancreatectomy in both the normal and alloxan diabetic dogs. Insulin treatment reduced an exaggerated response of total IRG in alloxan diabetic dogs. From these experiments, it is concluded that alloxan diabetic dogs have an increased response of plasma glucagon and extrapancreatic glucagon, which is reduced by insulin treatment. Furthermore, the difference in response of plasma glucagon to arginine in alloxan diabetic dogs and depancreatized dogs indicates that deficiency of insulin as well as pancreatic glucagon plays an important role in the secretion of extrapancreatic glucagon.