Relation between induction of rat hepatic ornithine decarboxylase activity by tumor promoters 12-O-tetradecanoylphorbol-13-acetate and phenobarbital and levels of the polyamines putrescine, spermidine and spermine, in vivo; differential effects of retinyl-acetate

A single i.p. injection of 12-O-tetradecanoylphorbol-13-acetate(TPA) induced a transient increase in the levels of rat liverputrescine, spermidine and spermine. These polyamine concentrationscontinuously increased until 6 h, immediately following administrationof the tumor promoter. Phenobarbital (PB) induced an increaseof the putrescine and spermidine concentrations during the 8h post administration studied, while spermine reached a plateauafter 4 h. When retinyl-acetate (RA) was injected one hour priorto TPA, the increases of the polyamines were considerably inhibited.This treatment with RA partially inhibited further increaseof putrescine and spermine by PB. These findings are discussedin respect to the concomitant ornithine decarboxylase (ODC)activities, we have previously reported. I.p. injection of RAalone caused an elevation of ODC activity as well as putrescineand spermidine concentration within 2 h of exposure.