Regulation of Adenylate Cyclase and Cyclic-AMP Dependent Protein Kinase Activities in A2-Cell Rich Guinea-Pig Islets of Langerhans

Abstract

Islets of Langerhans isolated from streptozotocin-treated guinea-pigs contain a majority of glucagon-producing A₂-cells. These islets have been used to study the activities of adenylate cyclase and protein kinase in the pancreatic A₂-cells. Both enzymes were present in the A₂-cell richt islets and possessed general characteristics similar to those of B-cell rich islet tissue. The A₂-cell adenylate cyclase was stimulated by adrenaline, and the protein kinase was stimulated in the presence of adrenaline and theophylline, agents which also increased glucagon release from guinea-pig islets. A major difference was therefore noted between the responses of the A₂-cells and B-cells to adrenaline, since adrenaline decreases the activity of adenylate cyclase and protein kinase in the B-cells. Nevertheless, both cell types responded to an elevation of adenylate cyclase and protein kinase activity with an increase in hormone secretion.