Effects of four organohalogen environmental contaminants on cytochrome P450 forms that catalyze 4- and 2-hydroxylation of estradiol in the rat liver.

The four environmental pollutants studied (3,3',4,4',5-pentachlorobiphenyl, 2,2',4,4'-tetrabromodiphenyl ether, Tris-(p-chlorophenyl)methanol, and 3,4,5-trichloroguaiacol) were all found to induce a significant increase in 4-hydroxylation of estradiol activity in male rat liver microsomes. However, only 3,3',4,4',5-pentachlorobiphenyl was found to significantly increase 4- and 2-hydroxylation of estradiol in female rat liver microsomes. 4-Hydroxylation has been suggested to be responsible for the development of estrogen-dependent tumors and, therefore, it cannot be excluded that these pollutants can be a risk for the development of estrogen-dependent tumors in humans and wildlife.