Time and dose dependencies for priming effect of glucose on insulin secretion

Abstract

Short-term exposure to glucose increases insulin secretion during subsequent stimulation. This priming effect of glucose was further investigated in the perfused rat pancreas. A 5-min pulse of 27.7 mM glucose enhanced the response to a second pulse of the sugar after a 5- or 30-min period of 3.9 mM glucose. With a 10-min pulse of 27.7 mM glucose, the priming effect tended to persist also after a 60-min but not after a 90-min rest period. The priming effects of glucose were also evaluated from enhancement of stimulation 15 min later with 3-isobutyl-1-methylxanthine (IBMX). A 10-min pulse of 8.3 and 27.7, but not 5.6 mM glucose enhanced IBMX-induced insulin secretion. Cycloheximide did not abolish the priming effect of glucose on IBMX-induced insulin secretion. Conclusions are: priming is rapidly induced; it persists longer than the time of induction; threshold concentrations of glucose that induce priming are similar to those that initiate insulin secretion; and mechanisms causing priming may not involve protein synthesis.