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The Nongenotoxic Hepatocarcinogens Diethylhexylphthalate and Methylclofenapate Induce DNA Synthesis Preferentially in Octoploid Rat Hepatocytes

AstraZeneca Central Toxicology Laboratory, Alderley Park, Macclesfield, Cheshire, United Kingdom

Ruth A. Roberts

AstraZeneca Central Toxicology Laboratory, Alderley Park, Macclesfield, Cheshire, United Kingdom

Diethylhexylphthalate (DEHP), a rodent carcinogen, and 1,4-dichlorobenzene (DCB), a noncarcinogen in rat liver, are potent hepatomitogens. We have reported previously that 7-day dosing with DEHP induced a higher bromodeoxyuridine labeling index (LI) in binuclear octoploid (2x4N) rat hepatocytes than did DCB, suggesting that induction of DNA synthesis in 2x4N hepatocytes might represent a more substantial carcinogenic risk. We compared 2 additional rodent hepatocarcinogens, methylclofenapate (MCP) and phenobarbitone, with ethylene thiourea (ETU), a noncarcinogenic hepatomitogen in rat. All 3 chemicals increased hepatic LI; the 8N population had the highest LI, but only the carcinogens increased LI in the 2x4N and 4N populations. To identify the target population for induction of DNA synthesis, we used a 1-hour pulse label at the peak of induction. The results were consistent with the 7-day data, and again the highest LI was in the 8N population. The nongenotoxic rodent carcinogens MCP and DEHP induced a significant increase in the LI in the 2x4N population, whereas ETU and DCB did not. These data support the hypothesis that increased DNA synthesis within the minority 2x4N population may be more significant for subsequent hepatocarcinogenesis.

Key Words: Methylclofenapate • 1,4-dichlorobenzene • ethylene thiourea • phenobarbitone • diethylhexylphalate • hepatocyte ploidy • nongenotoxic hepatocarcinogenesis • DNA synthesis

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Toxicologic Pathology, Vol. 28, No. 4, 503-509 (2000)
DOI: 10.1177/019262330002800401


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This Article Abstract Free Full Text (Free PDF) Free Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Hasmall, S. C. Articles by Roberts, R. A. Search for Related Content PubMed PubMed Citation Articles by Hasmall, S. C. Articles by Roberts, R. A. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB BIS(2-ETHYLHEXYL)PHTHALATE PHENYTOIN SODIUM Social Bookmarking                         What's this?