Enhanced cytochrome P450 (Cyp1b1) expression, aryl hydrocarbon hydroxylase activity, cytotoxicity, and transformation of C3H 10T1/2 cells by dimethylbenz(a)anthracene in conditioned medium.
The basal and benz(a)anthracene-induced aryl hydrocarbon hydroxylase activities of C3H 10T1/2 mouse embryo fibroblasts have been shown to vary with population growth. We report here that, in the case of dimethylbenz(a)anthracene, cytotoxicity and transformation (neoplastic/morphological transformation and focus formation) increased as a consequence of population growth and, at high cell densities, DNA adduct formation was elevated. Among the factors that may contribute to these changes, we have found that conditioning of the medium with population growth plays a significant role. Cells treated with medium conditioned by several days of cell growth supported increases in the dimethylbenz(a)anthracene induction of mRNA expression of a new mouse cytochrome P450 gene designated Cyp1b1, aryl hydrocarbon hydroxylase activity, cytotoxicity, and the frequency of neoplastic transformation. These results suggest a cause and effect relationship between the enhanced expression of Cyp1b1 due to medium conditioning and the enhanced expression of the cellular endpoints cytotoxicity and transformation.
Department of Radiological Health Sciences, Colorado State University, Fort Collins 80523.
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D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism*; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D001551:Benz(a)Anthracenes / Q000378:metabolism; D002452:Cell Count; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced* / Q000378:metabolism; D003470:Culture Media; D017077:Culture Media, Conditioned; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008809:Mice, Inbred C3H
D001551:Benz(a)Anthracenes; D003470:Culture Media; D017077:Culture Media, Conditioned; D015127:9,10-Dimethyl-1,2-benzanthracene; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; C030935:benz(a)anthracene; D001189:Aryl Hydrocarbon Hydroxylases; C585498:Cyp1b1 protein, mouse; D065633:Cytochrome P-450 CYP1B1