Inhibition of rat ovarian ornithine decarboxylase by ethanol in vivo and in vitro.

Intragastric administration of ethanol greatly inhibited ovarian ornithine decarboxylase (L-ornithine carboxy-lyase EC 4.1.1.17) stimulated by human chorionic gonadotropin in vivo. The inhibition occurred only if the treatment with ethanol was started before the injection of hormone. The use of inhibitors for alcohol dehydrogenase and aldehyde dehydrogenase clearly showed that the observed inhibition was a direct effect of ethanol itself. When rat ovarian cells were incubated in vitro with human chorionic gonadotropin the activity of ornithine decarboxylase was also markedly stimulated. This stimulation could also be inhibited by ethanol. Moreover, actinomycin D and alpha-amanitin inhibited the stimulation of ornithine decarboxylase, showing that the enhanced activity in vitro resulted from the synthesis of new mRNA for ornithine decarboxylase. The time dependence of the inhibition caused by ethanol addition resembled that after addition of actinomycin D. This supports the view that one site where ethanol inhibits protein synthesis is at the transcriptional level.