Several factors which stimulate the secretion of pancreatic glucagon have been reported by many authors based on the results mostly obtained in animal experiments. Since amino acids mixture is one of the most potent stimulators for glucagon secretion from the pancreas, the plasma response to arginine infusion in man was compared with those to other various stimuli.
Plasma glucagon was determined by the radioimmunoassay using an anti-glucagon serum, which is relatively specific for pancreatic glucagon but still cross-reacts with enteroglucagon.
The plasma glucagon level rose after the infusion of arginine for 30 minutes in amount of 300 ml of 10 per cent solution in normal subjects as well as in diabetic patients. Arginine infusion caused a rise in plasma glucagon in patients with hypoglycemia or other endocrine diseases. Whereas insulin induced hypoglycemia stimulates glucagon secretion in normal subjects, it did not cause any rise in plasma glucagon in diabetic patients. A rapid fall of blood glucose, cataglycemia, did not produce any change in the level of plasma glucagon. Plasma insulin rose after the injection of the tetrapeptide of human gastrin or secretin but the plasma glucagon response to these hormones was not observed at all. Pancreozymin, which is known as one of the most potent stimulators for the pancreatic secretion of glucagon or insulin in dogs, did not produce any rise in plasma glucagon nor insulin.
In comparison with the plasma response of glucagon to several stimuli, it is proved that only arginine infusion or insulin-induced hypoglycemia could produce an increase in plasma glucagon in the peripheral vein in normal subjects. In diabetic patients, however, insulin-induced hypoglycemia did not produce a marked increase in plasma insulin. Furthermore, it is dangerous to perform insulin test in patients with hypoglycemia. Therefore, our results suggest that arginine infusion test is the most useful among the several factors, which stimulate glucagon secretion from the pancreas in man.
