Insulin release from pancreatic islets of fetal rats mediated by leucine b-BCH, tolbutamide, glibenclamide, arginine, potassium chloride, and theophylline does not require stimulation of Ca super(2+) net uptake

In pancreatic islets of fetal rats the effect of glucose, glyceraldehyde, leucine, b-BCH, tolbutamide, glibenclamide, arginine, KCI and theophylline on super(45)Ca super(2+) net uptake and secretion of insulin was studied. All compounds tested failed to stimulate super(45)Ca super(2+) net uptake. However, in contrast to glucose and glyceraldehyde, leucine, b-BCH, tolbutamide, glibenclamide, arginine, KCl and theophylline significantly stimulated release of insulin. This effect could not be inhibited by the calcium antagonist verapamil. Elevation of the glucose concentration from 3 to 5.6 mM did not alter super(86)Rb super(+) efflux of fetal rat islets but inhibited super(86)Rb super(+) efflux of adult rat islets. Stimulation of super(86)Rb super(+) efflux with tolbutamide (100 mu g/ml), leucine (20 mM) or b-BCH (20 mM) in the presence of 3 mM glucose was also ineffective in fetal rat islets.