ETHANOLAMINE ANALOGS STIMULATE DNA-SYNTHESIS BY A MECHANISM NOT INVOLVING PHOSPHATIDYLETHANOLAMINE SYNTHESIS

Dimethylethanolamine (0.5-1 mM), added to serum-starved NIH 3T3 fibrob lasts, stimulated DNA synthesis 11-32-fold, and it also greatly enhanc ed the relatively modest (15-20-fold) mitogenic effect of insulin, Eth anolamine and momomethylethanolamine alone had no effects on DNA synth esis, but they also enhanced the stimulatory effect of insulin, althou gh less effectively than dimethylethanolamine did. Lower concentration s (2.5-5 mu g/ml) of compound D 609 (tricyclo-9-yl-xanthogenate), whic h had no effects on phospholipase activities, synergistically enhanced the combined effects of ethanolamine analogs and insulin on DNA synth esis without affecting the synthesis of ethanolamine phospholipids. Th ese results suggest that ethanolamine and its analogues, formed by pho spholipase D-mediated hydrolysis of ethanolamine phospholipids, may ha ve growth regulatory functions independent of their role as phospholip id precursors.