title: Summation of initiation activities of low doses of the non-hepatocarcinogen 1,2-dimethylhydrazine in the liver after carbon tetrachloride administration.
abstract: Summation of initiation by low doses of the indirect-acting non-hepatocarcinogen, 1,2-dimethylhydrazine (DMH) after proliferative stimulation with a necrogenic dose of carbon tetrachloride (CCl4) was investigated in terms of the induction of glutathione S-transferase placental form (GST-P) positive liver cell foci. Cell kinetics of liver after CCl4 i.g. treatment were examined with bromodeoxyuridine (BrdU) labeling (experiment I). To assess the correlation between cell proliferation and induction of liver cell foci, DMH (10 mg/kg i.g.) was administrated to 7-week-old male F344 rats at 12, 24, 36, 48, 60, 96 h after CCl4 i.g. and initiated populations expanded using the resistant hepatocyte model (experiment IIA). Subsequently, effects of repeated administration (10 mg/kg, four times, i.g.) of DMH were compared with the results of a single administration (40 mg/ kg, i.g.) with the same total dose (experiment IIB). In experiments I and IIA, the numbers and areas of GST-P-positive foci increased with the BrdU labeling index at the time of DMH treatment (maximum after 60 h). In experiment HB, repeated exposure of DMH at 10 mg/kg, four times resulted in significant (P<0.05) increase in number and area of GST-P-positive foci compared with the single administration (40 mg/kg). Thus, multiple low dose treatments during cell proliferation might be most effective for detection of weak initiation activity.
authors.affiliation: Laboratory of Pathology, Aichi Cancer Center Research Institute, Kanokoden, Nagoya, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sakai
authors.forename: T
authors.initials: T
authors.lastname: Tsukamoto
authors.forename: M
authors.initials: M
authors.lastname: Yamamoto
authors.forename: T
authors.initials: T
authors.lastname: Yanai
authors.forename: T
authors.initials: T
authors.lastname: Masegi
authors.forename: K
authors.initials: K
authors.lastname: Inada
authors.forename: H
authors.initials: H
authors.lastname: Nakanishi
authors.forename: M
authors.initials: M
authors.lastname: Tatematsu
mesh_terms: D019813:1,2-Dimethylhydrazine / Q000008:administration & dosage* / Q000633:toxicity*; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D002251:Carbon Tetrachloride / Q000633:toxicity*; D002273:Carcinogens / Q000008:administration & dosage / Q000633:toxicity*; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D005982:Glutathione Transferase / Q000096:biosynthesis; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000201:enzymology / Q000473:pathology; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors
chemical_list: D002273:Carcinogens; D004247:DNA; D002251:Carbon Tetrachloride; D005982:Glutathione Transferase; D001973:Bromodeoxyuridine; D019813:1,2-Dimethylhydrazine