title: Initiation of cell proliferation in livers of the viviparous fish Poeciliopsis lucida with 7,12-dimethylbenz[a]anthracene.
abstract: Stimulation of liver cell proliferation by sublethal exposures to 7,12-dimethylbenz[a]anthracene (DMBA) is examined in the small, viviparous fish Poeciliopsis lucida. Poeciliopsis is susceptible to induction of liver tumors by repeated short-term exposures, under 24 hr, to waterborne DMBA at 5 ppm. Exposures to 5 ppm for 24 hr was lethal to fish under 1 month old and resulted in 60% mortality of adult females 20-25 mm in length. Response to 16-, 20-, and 22-hr exposures of 5 ppm DMBA, as measured by mitotic index, was similar in females of two size classes, 20-25 mm and 26-30 mm. Differences were observed in the onset of mitosis in livers of fish exposed for 16 hr vs 20 or 22 hr. Hepatocyte proliferation did not begin until 10-11 days after the 16-hr exposure and lasted for only 3 days. When exposure was increased to 20 or 22 hr, mitotic activity was observed earlier, 2 days following treatment, and continued for 6-8 days. The peak period of cell proliferation also varied, occurring 12 days after a 16-hr exposure, 4 days after a 20-hr exposure, and at least 10 days after a 22-hr exposure. The mitotic index was the highest on the final day specimens of the 22-hr treatment were collected. These results suggest that the toxic properties of DMBA in stimulating cell proliferation may function as an important cofactor in hepatocarcinogenesis.
authors.affiliation: NIEHS Marine and Freshwater Biomedical Core Center, University of Connecticut, Storrs 06268.
authors.forename: M E
authors.initials: ME
authors.lastname: Schultz
authors.forename: L A
authors.initials: LA
authors.lastname: Kaplan
authors.forename: R J
authors.initials: RJ
authors.lastname: Schultz
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity*; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D003532:Cyprinodontiformes / Q000502:physiology*; D005260:Female; D008099:Liver / Q000166:cytology / Q000187:drug effects*; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced; D008938:Mitosis / Q000187:drug effects; D013997:Time Factors
chemical_list: D015127:9,10-Dimethyl-1,2-benzanthracene