Role of Glucagon and Somatostatin in Insulin Release

The role of endogenous glucagon and somatostatin in insulin release was studied. Islets isolated from adult rats were incubated for 60 min in 3.3, 8, 3 and 16.7 mM glucose with anti-glucagon antiserum (AGA) or anti-somatostatin antiserum (ASA) which was produced in rabbits. For the control experiments the antiserum was replaced by normal rabbit serum (NRS). Insulin release from islets treated with AGA was suppressed in 3.3 and 8.3 mM glucose as compared to islets treated with NRS, while insulin release was not affected in 16.7 mM glucose. On the other hand, insulin release from islets treated with ASA was enhanced in 3.3 and 8.3 mM glucose as compared to that from islets treated with NRS, whereas in 16.7 mM glucose it was not different from the control. These observations indicate that endogenous glucagon and somatostatin play a physiological role in the regulation of insulin release, but their regulation of insulin release is deranged at non-physiologically high glucose concentrations.