Promitogenic effects of ethanol, methanol, and ethanolamine in insulin-treated fibroblasts

The zinc-dependent potentiating effect of ethanol (EtOH) on insulin-stimula ted DNA synthesis was studied with a locus on the possible site of EtOH act ion and the ability of other alcohols to elicit similar promitogenic effect s. In serum-starved (27 hr) NIH 3T3 fibroblasts, 200-300 mM methanol (MeOH) and 0.1-1.5 mM ethanolamine (Etn), but not 3- to 9-carbon normal alcohols, enhanced the effect of insulin on DNA synthesis to varying extents. The pr omitogenic effects of EtOH and MeOH, but not that of Etn, required the pres ence of 15-25 mu M zinc. The potentiating effects of Etn were enhanced by 5 mM choline (Cho) and inhibited by 1-3 mM hemicholinium-3 (HC-3), an inhibi tor of Cho transporter and Cho kinase. In the presence of 15 mu M zinc, 40 mM EtOH, which had no effect on its own, inhibited the potentiating effects of Cho and enhanced the inhibitory effects of HC-3 on synergistic stimulat ion of DNA synthesis by Etn and insulin. On the other hand, both Cho and HC -3 partially inhibited the promitogenic effect of 80 mM EtOH in the presenc e of 25 mu M zinc. After a 10-min incubation, EtOH decreased the amount of cell-associated [C-14]Cho in the absence but not in the presence of HC-3. A fter a 40-min incubation, Cho (5 mM) partially inhibited the cellular uptak e as well as the metabolism of [C-14]Etn. Whereas after the 40-min incubati on 80 mM EtOH had no effects on Etn metabolism in the absence of Cho it dec reased the amount of cell-associated [C-14]Etn. However, EtOH had no detect able effects on cell association of [C-14]Een after the 10-min incubation. The results suggest that in NIH 3T3 fibroblasts EtOH is a remarkably specif ic promitogen, and that it may act via a cell membrane site(s), also regula ted by Cho (agonist) and HC-3 ((antagonist), which can influence membrane b inding and the promitogenic activity of Een. (C) 2000 Elsevier Science Inc.