Effect of cold stress on expression of genes for the AhR-dependent pathway of CYP1 regulation in rat liver.

The level of mRNA for cytochromes P450 (CYP1A1, CYP1A2, and CYP1B1) and CYP1 regulatory proteins (heat shock protein, aryl hydrocarbon receptor, aryl hydrocarbon receptor repressor, and aryl hydrocarbon receptor nuclear translocator) was measured in the liver of rats after cold stress (4 degrees C). The CYP1A1 mRNA level increased and remained high for 10 days after 5-day cold exposure. The level of mRNA for CYP1A2, heat shock protein, and aryl hydrocarbon receptor nuclear translocator decreased by the 10th day. The level of mRNA for CYP1B1, aryl hydrocarbon receptor, and aryl hydrocarbon receptor nuclear translocator remained unchanged over this period.