Correlation of Placenta! Microsomal Activities with Protein Detected by Antibodies to Rabbit Cytochrome P-450 Isozyme 6 in Preparations from Humans Exposed to Polychlorinated Biphenyls, Quaterphenyls, and Dibenzofurans

Placenta! tissues were obtained from Chinese women in Tai wan who had been exposed to contaminated rice oils containing polychlorinated biphenyls and their thermal degradative prod ucts. Exposure via the diet occurred 4-5 years prior to preg nancy. Placental microsomal fractions from eight of the nine exposed subjects studied showed marked elevation of benzo(a)pyrene hydroxylation and 7-ethoxyresorufin 0-deethylation activities relative to control subjects. Placental microsomes from exposed subjects were found to contain a protein that cross-reacted with antibodies raised to rabbit cytochrome P-450 isozyme 6, an isozyme induced by polycyclic aromatic hydrocar bons. This protein was not observed with microsomal samples from control subjects. A significant correlation was found be tween the relative amounts of the immunoreactive protein and benzo(a)-pyrene hydroxylation and 7-ethoxyresorufin 0-deethylation activities. The 7-ethoxyresorufin 0-deethylation activities were inhibited by a-naphthoflavone, a compound known to inhibit activities of rabbit cytochrome P-450, isozyme 6.