The stimulus-secretion coupling of glucose-induced insulin release. I. Interaction of epinephrine and alkaline earth cations.

Abstract

Abstract Omission of Ca ++ or high Mg ++ concentrations inhibits the stimulant action of glucose upon insulin secretion by incubated pieces of rat pancreatic tissue. Addition of Ba ++ to the incubation medium restores a normal rate of secretion both in the absence of Ca ++ and at high Mg ++ concentrations. These data suggest that Mg ++ on the one hand, and Ca ++ or Ba ++ on the other might act as antagonists upon the secretory process. Inhibition of glucose-induced insulin secretion by epinephrine is not overcome by theophylline or dibutyryl-adenosine cyclic monophosphate, suggesting that this inhibition does not result solely from a decrease in the cellular concentration of adenosine cyclic monophosphate. Neither Ba ++ nor Ca ++ modify the inhibitory effect of epinephrine. It is hypothesized that Ca ++ influx in the beta-cell might trigger the release of insulin and that epinephrine might suppress insulin secretion by blocking such influx.