Influences of different polychlorinated biphenyls on cytocidal, mitoinhibitory, and nodule-selecting activities of N-2-fluorenylacetamide in rat liver.
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 microM), 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 microM; CAS: 53-95-2). By comparison, pretreatments with either the PB-type or MCA-type PCB's (50-200 mumol/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 gamma-glutamyltranspeptidase-positive (gamma-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 mumol/kg by gavage 10 days after DENA and 7 days before 2-FAA, all reduced the size of 2-FAA-selected gamma-GT+ nodules during the 4-week period after PH. These results indicate that, in spite of predictable inducer-specific 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.
Hayes
M A
MA
Roberts
E
E
Safe
S H
SH
Farber
E
E
Cameron
R G
RG
D015073:2-Acetylaminofluorene / Q000378:metabolism / Q000633:toxicity*; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D006498:Hepatectomy; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008113:Liver Neoplasms / Q000139:chemically induced; D008115:Liver Regeneration / Q000187:drug effects; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D010634:Phenobarbital / Q000494:pharmacology; D011078:Polychlorinated Biphenyls / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344; D005723:gamma-Glutamyltransferase / Q000032:analysis
D008748:Methylcholanthrene; D015073:2-Acetylaminofluorene; D011078:Polychlorinated Biphenyls; D005723:gamma-Glutamyltransferase; D010634:Phenobarbital