Effects of individual polychlorinated naphthalene (PCN) components of Halowax 1051 and two defined, artificial PCN mixtures on AHR and CYP1A1 protein expression, steroid secretion and expression of enzymes involved in steroidogenesis (CYP17, 17β-HSD and CYP19) in porcine ovarian follicles

Abstract In this study we tried to answer a question which component of Halowax 1051 is responsible for, observed in previously published study, androgenic effects of the mixture, and whether it is possible to draw conclusions about the action of mixtures by examining the effect of an indicator congener. Ovarian follicles were incubated with individual congeners of an artificial mixture for 6–24 h. At the end of the incubation period, media were collected for determination of progesterone (P4), androstenedione (A4), testosterone (T) and estradiol (E2) levels by enzyme immunoassay, and follicles were retained for an examination of aryl hydrocarbon receptor (AHR), cytochrome p450 enzymes (CYP1A1, CYP17, CYP19), and 17β-hydroxysteroid dehydrogenase (17β-HSD) protein expression by Western blotting. CN73 in dose 50 pg/ml after 6 h had no effect and decreased AHR expression after 24 h, while at dose 400 pg/ml increased AHR protein expression after 6 h of exposure which remained elevated after 24 h. CN74 and CN75 at both concentrations tested (25 and 50 pg/ml) stimulated AHR protein expression after 6 h and decreased it after 24 h of exposure. Individual congeners induced a rapid increase in CYP1A1 protein expression, with a rank order of efficacy of CN73 > CN74 = CN75. All congeners increased P4/A4 and T/E2 secretion ratios in association with a decrease in the A4/T ratio, pointing to androgenic and anti-estrogenic properties of PCNs in ovarian follicles. The most potent congener in this context was CN73. The effects of mixtures were comparable to those of CN74 and CN75, and were not as strong as those observed for CN73. Collectively, these data suggest antagonistic actions of single congeners in a mixture, indicating that the actions of a mixture cannot be predicted based on the actions of individual congeners.