Inhibition of Glucose-Induced Insulin Secretion in Trypsin-Treated Islets of Langerhans

Abstract

A method is described for the preparation of single cells from isolated rat islets by treatment of the islets with a Ca²⁺, Mg²⁺-free buffer and mild shearing forces. In these cells insulin secretion can be stimulated with sulfonylureas, but not with glucose. In cells prepared by an additional trypsin treatment both stimulants are ineffective. Pretreatment of intact islets with trypsin inhibits glucose-induced insulin secretion, whereas tolbutamide-induced insulin release is unaffected. Pretreatment of islets with Ca²⁺ , Mg²⁺ -free buffer also inhibits glucose induced insulin release during the subsequent incubation in the presence of divalent cations. These results indicate, that the morphological integrity of the islets is no prerequisite to insulin release. The sensitivity of glucose-induced insulin release to trypsin treatment of the islets further supports the glucoreceptor model.