EFFECTS OF NICOTINAMIDE ON CLONAL RAT INSULINOMA CELL-PROLIFERATION, POLYAMINE CONTENT AND INSULIN-SECRETION

Tumoral insulin - secreting cells (RINm5F) were cultured for 4 days wi th nicotinamide, a poly (ADP - ribose) synthetase inhibitor. This resu lted in a dose - dependent inhibition of the cellular proliferation ra te, along with a modest decrease in cell viability. Nicotinamide faile d to affect the cellular insulin content, but reduced the insulin secr etion into the culture medium. Nicotinamide treatment furthermore redu ced the cellular content of polyamines, compounds seemingly involved i n regulation of the-growth and function of insulin - producing cells. Restoration of the decreased polyamine content by the concomitant addi tion of the polyamine precursor putrescine failed to influence the dec reased proliferation rate and insulin secretion, indicating that the i nhibitory effects of nicotinamide on these functions cannot be ascribe d to the decrease in polyamine content.