Stimulus-secretion coupling of arginine-induced insulin release. Insulinotropic action of agmatine

Agmatine causes a concentration-related (0.1-1.0 mM) stimulation of insulin secretion by rat pancreatic islets exposed to D-glucose (5.6-11.1 mM) but, like L-arginine, fails to affect insulin release either in the absence of glucose or at a high concentration (16.7 mM) of the hexose. Agmatine, which accumulates in islet cells, also stimulates 45Ca net uptake by the islets. The secretory response to agmatine represents a delayed process. It is enhanced by theophylline and suppressed by antimycin A or the absence of extracellular Ca2+. The insulinotropic action of agmatine is compatible with the view that endogenously formed polyamines may play a role in the secretory response of islet cells to L-arginine.