FACTORS CONTROLLING GLUCAGON SECRETION

Abstract

This chapter describes the factors controlling glucagon secretion. Glucagon secretion has been investigated using isolated tissues, isolated perfused organs, in situ organs, or entire organisms isolated tissues include pancreas slices as such, or slices from a duct-ligated pancreas, and isolated islets of Langerhans prepared either by microdissection, or by collagenase digestion of pancreatic pieces. Isolated organs systems use isolated rat, dog pancreas, or stomach, preparations which are perfused by artificial media, or blood. Appropriate catheterizations permit simultaneous measurements of blood flow, and net pancreatic, or gastric glucagon production in large animals such as the dog or the pig. At the level of the whole organism, samples can be taken at the portal vein, or peripherally, and in this last instance, one should remember that liver glucagon uptake may represent 30%-85% of liver glucagon inflow. There is evidence that glucose entry into the A cell may require insulin and, it has been demonstrated that insulin simultaneously increases glucose utilization by the A cells, augments their ATP formation and permits glucose to inhibit glucagon secretion.