Insulin release. Demonstration of a priming effect of 3-isobutyl-1-methyl-xanthine (IBMX) on islets of Langerhans.

Exposure of isolated rat pancreatic islets to 1 mM 3-isobutyl-1-methyl-xanthine (IBMX) resulted in a 5.7-fold increase in the rate of insulin release. After a 30-min rest period under basal conditions, reexposure of the islets to 1 mM IBMX resulted in an enhanced rate of release when compared with either a timed control -islets simultaneously exposed to IBMX for the first time-or with the first priming response to IBMX. The possibility of a continuous priming effect was suggested by the gradually rising rate of insulin release during exposure to IBMX. It is concluded that islets have a memory for IBMX exposure that results in increased responsiveness to subsequent stimulation by IBMX.