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M. Anthony Hayes, Esther Roberts, Stephen H. Safe, Emmanuel Farber, Ross G. Cameron, Influences of Different Polychlorinated Biphenyls on Cytocidal, Mitoinhibitory, and Nodule-Selecting Activities of N-2-Fluorenylacetamide in Rat Liver, JNCI: Journal of the National Cancer Institute, Volume 76, Issue 4, April 1986, Pages 683–691, https://doi.org/10.1093/jnci/76.4.683
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Abstract
The influences of different polychlorinated biphenyl (PCB) isomers and congeners on distinct hepatotoxic responses to the hepatocarcinogen N-2-fluorenylacetamide [(2-FAA) CAS: 53-96-3] were examined in F344 rats. Cytocidal toxicity of 2-FAA (25–400 µM), determined by lactate dehydrogenase release during 20 hours in primary monolayer cultures of isolated rat hepatocytes, was reduced by in vivo pretreatment with either phenobarbitone [(PB) CAS: 50-06-6] or 2,2′,4,4′,5,5′-hexachlorobiphenyl (HCBP), a PB-type PCB inducer. However, cytocidal toxicity of 2-FAA was substantially potentiated by either 3-methylcholanthrene [(MCA) CAS: 56-49-5] or 3,3′,4,4′-tetrachlorobiphenyl [(TCBP) CAS: 32598-13-3], an MCA-type PCB. In the same cell culture assays, all four pretreatments similarly reduced cytocidal toxicity of N-hydroxy-N-2-fluorenylacetamide (0.32–32 µM; CAS: 53-95-2). By comparison, pretreatments with either the PB-type or MCA-type PCB's (50–200 µmol/kg) diminished mitoinhibitory toxicity of 2-FAA in vivo, as measured by hepatic regenerative growth and hepatocyte labeling indices 7 days after partial hepatectomy (PH) in rats given 3 consecutive daily doses of 2-FAA (20/mg/kg/day) before PH. This regimen of 2-FAA and PH promoted rapid selective growth of γ-glutamyltranspeptidase-positive (γ-GT+) nodules at 2 and 4 weeks after PH in rats previously given an initiating hepatocarcinogen, diethylnitrosamine [(DENA) CAS: 55-18-5]. However, various PCB's, including 2,2′,4,4′,5,5′-HCBP, 3,3′,4,4′-TCBP, 2,2′,4,4′-TCBP, 2,2′,5,5′-TCBP, and the commercial mixture Aroclor 1254, each given as a single dose of 50 µmol/kg by gavage 10 days after DENA and 7 days before 2-FAA, all reduced the size of 2-FAA-selected γ-GT+ nodules during the 4-week period after PH. These results indicate that, in spite of predictable inducerspecific opposite influences of different types of PCB's on cytocidal toxicity of 2-FAA, all PCB's similarly reduce nodule selection by 2-FAA in initiated livers. Reduced growth of 2-FAA-selected nodules correlated with the consistent ability of all PCB's to enhance regeneration of liver mass after 2-FAA and PH.
