Congener-specific accumulation of polychlorinated biphenyls in ovarian follicular wall follows repeated exposure to PCB 126 and PCB 153. Comparison of tissue levels of PCB and biological changes

OBJECTIVE: Small (SF), medium (MF) and large (LF) preovulatory porcine follicles were isolated and incubated in an Erlenmeyer flask containing 5 ml of medium with addition of PCB 126 or PCB 153 to test differences in their accumulation in the follicular wall. METHODS; The follicles were incubated in M199 medium at 37 degrees C with constant shaking at 70 rpm, for 6 days. The media were changed every day and repeated dose 25 pg/ml of PCB 126 or 25 ng/ml of PCB 153 was added each day till 6 days of culture. Media were collected every day and frozen for steroid analysis by RIA. 24 h after the last treatment follicles were frozen for further polychlorinated biphenyls (PCB) content analysis. PCB concentrations in the follicular wall were analysed by mass spectrometry. RESULTS: 3.3%; 3.6% and 5.6% of total PCB 126 dose, and 71%; 71.4% and 30.4% of total PCB 153 dose accumulated in SF, MF and LF follicles, respectively. The accumulative effect of PCB was manifested by the disruption of estradiol (E2) secretion. In SF antiestrogenic action of PCB 126 was observed during the whole time of exposure while PCB 153 decreased E2 till 4 days of culture and then estrogenic action was observed. In MF, both these congeners decreased E2 till 5 days of exposure and then estrogenic actions were noted with the highest magnification in the case of PCB 126. In LF both PCB studied increased E2 till 3 days of exposure with the highest magnification of PCB 126, then antiestrogenic action was noted. Testosterone secretion was generally affected in a pattern oposite to that of E2 suggesting action on P450arom activity. CONCLUSION: The results of these studies demonstrated that disruption of aromatization process in the follicles following repeated exposure to both congeners is not directly correlated with the bioaccumulation or amount of PCB within the follicular wall.