Induction cytochrome

Yeast is of exceptional value in the study of cytochrome regulation. It is a facultative anaerobe, and the usual cytochromes disappear under anaerobic conditions. On aeration, cytochrome induction can be demonstrated in the living cell, and the role of oxygen and carbon source, as well as the effect of inhibitors, can be evaluated by a variety of means [19-25], Yeast affords opportunities for genetic analysis and lends itself to studies of the inheritance of nuclear factors governing cytochrome synthesis. Moreover, this organism readily develops a mitochondrial abnormality on treatment with acriflavine, the petite mutation, which permits examination of the role of cytoplasmic inheritance [26]. 

The toxicology of PCBs is complex and not fully understood. Coplanar PCBs interact with the Ah-receptor, with consequent induction of cytochrome P4501A1/2 and Ah-receptor-mediated toxicity. Induction of P4501A1 provides the basis of valuable biomarker assays, including bioassays such as CALUX. Certain PCBs, for example, 3,3, 4,4 -TCB, are converted to monohydroxymetabolites, which act as thyroxine antagonists. PCBs can also cause immunotoxicity (e.g., in seals). 

Coplanar PCBs, PCDDs, and PCDFs express Ah-receptor-mediated toxicity (Chapter 6, Section 6.2.4). Binding to the receptor leads to induction of cytochrome P4501 and a number of associated toxic effects. Again, toxic effects are related to the extent of binding to this receptor and appear to be additive, even with complex mixtures of planar polychlorinated compounds. Induction of P4501A1/2 has been widely used as the basis of a biomarker assay. Residue data can be used to estimate TEQs for dioxin (see Chapter 7, Section 7.2.4). 

Fish hepatocyte lines have also been developed, which can show cytochrome P450 lAl induction due to PAHs and planar polychlorinated aromatic compounds binding to the Ah receptor (Vaillant et al. 1989, Pesonen et al. 1992). 

Monod, G. (1997). L induction du cytochrome P450 lAl. In Biontarquers en Ecotoxicologie Aspects Fondamentaux. Paris Masson, 33-51. 

Rattner, B.A., Melancon, M.J., and Custer, T.W. et al. (1993). Biomonitoring environmental contamination with pipping black-crowned night heron embryos induction of cytochrome P450. Environmental Toxicology and Chemistry 12, 1719-1732. 

Vaillant, C., Monod, G., and Volataire, Y. et al. (1989). Measurement and induction of cytochrome P450 and monooxygenases in a primary culture of rainbow trout hepatocytes. Comptes Redus de L Academic des Sciences 308, 83-88. 

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