In a group of pancreatectomized subjects, immunoreactive glucagon (IRG) concentrations were normal after an overnight fast, increased after oral glucose, were not suppressed by somatostatin (SRIF) or insulin, and in two of four subjects they rose with an arginine infusion. Even though the SRIF infusion failed to lower IRG, there was a fall in plasma glucose concentration in both subjects. In two subjects, endogenous hyperglycemia occurred during insulin withdrawal without a rise in IRG, and, in one subject, mild diabetic ketoacidosis developed with only a minimal rise in IRG.
These results support the presence of an extrapancreatic source of IRG in man. Secretion from these extrapancreatic alpha cells appears to be regulated differently than secretion from pancreatic alpha cells.
