Promoting effects of phenobarbital and 3′-methyl-4-dimethylaminoazobenzene on the appearance of γ-glutamyltranspeptidase positive foci in rat liver pretreated with varying doses of diethylnitrosamine

Abstract

The promotion potential of phenobarbital (PB) and 3′-methyl-4-dimethylaminoazobenzene (3′-Me-DAB) on liver carcinogenesis after initiation with various doses of diethylnitrosamine (DEN) was assessed using an in vivo short term system. Male F344 rats were pretreated with a single intraperitoneal injection of varing doses of DEN (0, 6, 12, 25, 50, 100 or 200 mg/kg body wt), and 2 weeks later were treated with 0.05% PB or 0.06% 3′-Me-DAB for 6 weeks. All animals were subjected to partial hepatectomy 3 weeks after the DEN treatment. Quantitation of γ-glutamyltranspeptidase-positive (γ-GT +) foci revealed a DEN dose-dependent response. Magnitude of promotion by PB and more pronounced by 3′-Me-DAB was, in contrast, strongest at the lower doses of DEN. The results suggest that quantitative diffeences with regard to initiation level may exist, influencing the promotability of initiated cells.