Effect of Arsenite on Induction of CYP1A and CYP2H in Primary Cultures of Chick Hepatocytes
| Autor: | Judith M. Jacobs, Maurice Roberts, Robert R. Roussel, Jacqueline F. Sinclair, Barney E. Dwyer, Peter R. Sinclair, Sheryl G. Wood, Doreen Marek, Heidi S. Walton |
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| Rok vydání: | 1998 |
| Předmět: |
Sodium arsenite
Arsenites Chick Embryo Heme Toxicology chemistry.chemical_compound Cytochrome P-450 Enzyme System Cytochrome P-450 CYP1A1 medicine Animals Cytochrome P-450 Enzyme Inhibitors Inducer RNA Messenger Cells Cultured Arsenite Pharmacology Biliverdin biology Cytochrome P450 Oxidoreductases N-Demethylating Sodium Compounds Molecular biology Rats Heme oxygenase medicine.anatomical_structure Liver chemistry Enzyme Induction Phenobarbital Hepatocyte Heme Oxygenase (Decyclizing) biology.protein |
| Zdroj: | Toxicology and Applied Pharmacology. 150:376-382 |
| ISSN: | 0041-008X |
| DOI: | 10.1006/taap.1998.8436 |
| Popis: | In earlier studies, treatment with sodium arsenite was shown to decrease total hepatic CYP in rats. A concomitant increase in heme oxygenase, the rate-limiting step in heme degradation to biliverdin, was considered responsible for the decrease in CYP. Here we investigated the effect of sodium arsenite on induction of CYP2H, CYP1A, and heme oxygenase in primary cultures of chicken embryo hepatocytes. When added simultaneously with inducer, arsenite inhibited phenobarbital-mediated increases in CYP2H and 3-methylcholanthrene-mediated increases in CYP1A, as measured enzymatically and immunochemically. Near maximal decreases were observed in these forms of CYP at a concentration of 2.5 microM sodium arsenite. The concentration-dependent decreases in CYP2H and CYP1A by sodium arsenite were concomitant with increases in heme oxygenase. Sodium arsenite was not toxic at concentrations as high as 10 microM, as indicated by protein synthesis and the reduction of MTT by intact cells. Sodium arsenite had no effect on induction of CYP2H1 mRNA, suggesting that the decreases in this form of CYP occurred post-transcriptionally. Treatment of cells with tin mesoporphyrin (SnMeso), an inhibitor of heme oxygenase, resulted in inhibition of arsenite-induced heme oxygenase. However, SnMeso did not alter the effect of arsenite to prevent phenobarbital-mediated increases in CYP2H protein. SnMeso alone inhibited phenobarbital-mediated increases in CYP2H. Inclusion of 2 or 5 microM exogenous heme with arsenite did not prevent the arsenite-mediated decrease in CYP2H. Combined treatment with heme and phenobarbital induced heme oxygenase to the same extent as treatment with heme, arsenite, and phenobarbital. However, CYP2H activity was decreased only when the treatment included arsenite. These results suggest that elevated levels of heme oxygenase alone are not responsible for arsenite-mediated decreases in CYP2H. |
| Databáze: | OpenAIRE |
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