The Stimulus-Secretion Coupling of Glucose-Induced Insulin Release. XV. Participation of Cations in the Recognition of Glucose by the β-Cell1

Abstract

Glucose-induced (pro)insulin synthesis by isolated islets is either unaffected or slightly increased at high Mg²⁺ and low Ca²⁺ concentrations, whereas the release of preformed and newly synthesized hormonal peptides is markedly depressed under the same conditions. These findings indicate that the major effect of alkaline earth cations on insular function is related to a terminal event in the insulin-releasing sequence. In contrast, extracellular acidosis or the replacement of large amounts of Na⁺ by K⁺, Li⁺ and Tris caused a concomitant reduction of glucoseinduced insulin biosynthesis, calcium uptake and subsequent insulin release by the islets, suggesting that the insular glucosensor mechanism involves a sodium-dependent step of glucose handling by the β-cell. (Endocrinology93: 1012, 1973)