Effect of 6-aminonicotinamide on insulin release and C-14 glucose oxidation by isolated pancreatic rat islets: difference between glucose, tolbutamide and aminophylline.

Abstract

Collagenase—isolated pancreatic islets collected from adult rats were incubated with glucose, tolbutamide or aminophylline (a soluble salt of theophylline). Indices of activity were insulin released into the medium, and oxidation of glucose labeled either in the C–l or C–6 position. Whereas glucose alone (16.5mM) produced a highly significant increase in insulin release, tolbutamide (0.1 mg/ml) or aminophylline (1 or 10mM) were ineffective by themselves. Both, however, potentiated the effect of glucose. If production of 14–CO2 from labeled glucose (SA 1.0 μi/mg) was measured in the presence of glucose, addition of neither tolbutamide nor aminophylline changed the number of 14–CO2 counts. If the islets were obtained from animals pretreated with 6–Aminonicotinamide, glucose released significantly less insulin, and less C–l carbon was incorporated into 14–CO2, indicating possible interference with adequate functioning of the pentose phosphate shunt. Addition of tolbutamide did not restimulate oxidation of gl...