title: gamma-Glutamyltranspeptidase-positive rat hepatocytes are protected from GSH depletion, oxidative stress and reversible alterations of collagen receptors.
abstract: The aim of this study has been to define cytotoxic mechanisms that may cause clonal expansion in the liver of pre-carcinogenic cells. An in vitro model, which has been described previously, was used. Hepatocytes were isolated from carcinogen-treated rats and a high proportion of the cells were gamma-glutamyltranspeptidase (GGT)-positive. The cells were incubated in suspension and exposed to toxic agents in concentrations that induced a moderate increase in cellular leakage within 3 h. Samples were withdrawn and sampled cells were then allowed to attach to collagen-coated plates. Attached cells were stained and the ratio of GGT-positive/GGT-negative cells (GGT-ratio) was determined. The initial GGT-ratio was 10.4 +/- 4.7% and an increased ratio was taken as a sign of toxicity that resulted in a selection of GGT-positive cells. In a first series of experiments it was shown that hydroquinone and menadione increase the GGT-ratio, while diquat, sodium selenite, diethyl maleate or phorone do not. However, diethyl maleate in combination with diquat increased the GGT-ratio. Hydrogen peroxide (5 mM) increased the GGT-ratio as effectively as hydroquinone (0.3 mM). Lower concentrations of H2O2 (0.05 mM) increased the GGT-ratio in GSH-depleted cells. The changes induced by hydroquinone and H2O2 in low concentration were reversible. In another series of experiments, plates coated with antibodies against beta 1-integrin were used. An increase in the GGT-ratio was obtained with anti beta 1-integrin, but not with broad spectrum anti-rat hepatocyte or anti-rat beta 2-microglobulin antibodies as substrata. These data suggested an involvement of the beta 1-integrin in the selection. Taken together, these data indicate that GGT-positive hepatocytes are protected against GSH depletion and oxidative stress that may result in reversible receptor alterations.
authors.affiliation: Department of Toxicology, Institute of Occupational Health, 84 Solna, Sweden.
authors.forename: U
authors.initials: U
authors.lastname: Stenius
authors.forename: K
authors.initials: K
authors.lastname: Rubin
authors.forename: D
authors.initials: D
authors.lastname: Gullberg
authors.forename: J
authors.initials: J
authors.lastname: Högberg
mesh_terms: D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis*; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D004052:Diethylnitrosamine / Q000633:toxicity; D004178:Diquat / Q000494:pharmacology; D005260:Female; D005978:Glutathione / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006873:Hydroquinones / Q000494:pharmacology; D007659:Ketones / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D008298:Maleates / Q000494:pharmacology; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D038981:Receptors, Collagen; D012643:Selenium / Q000494:pharmacology; D018038:Sodium Selenite; D014812:Vitamin K / Q000494:pharmacology; D005723:gamma-Glutamyltransferase / Q000032:analysis*
chemical_list: D014408:Biomarkers, Tumor; D006873:Hydroquinones; D007659:Ketones; D008298:Maleates; D011956:Receptors, Cell Surface; D038981:Receptors, Collagen; D014812:Vitamin K; D004052:Diethylnitrosamine; C018637:phorone; D003094:Collagen; D004178:Diquat; D006861:Hydrogen Peroxide; D005723:gamma-Glutamyltransferase; C014476:diethyl maleate; D005978:Glutathione; D012643:Selenium; D018038:Sodium Selenite; D010634:Phenobarbital