Effect of polychlorinated biphenyls on the secretion of oxytocin from luteal and granulosa cells in cow: possible involvement of glucocorticoid receptors

Polychlorinated biphenyls (PCBs) stimulate oxytocin secretion from bovine granulosa and luteal cells. Since oxytocin on the one hand is released from ovarian cells by cortisol and on the other hand PCBs can be bound by glucocorticoid receptors (GCr), we have tested the hypothesis that PCBs acting via GCr can stimulate oxytocin secretion. In preliminary studies the effect of RU486 (GCr blocker) on cells viability was tested. Thereafter, a selected dose of RU486 (105M), which did not affect cell viability, was used in further experiments. It appears that this dose of RU486 completely blocked GCr against cortisol-stimulated oxytocin secretion, in both types of cells. Furthermore, granulosa cells (105) from follicles of two sizes (>1 cm < in diameter) and luteal cells (105) from day 5–10 of estrous cycle were incubated for 72 h with congeners of PCB (126, 77 or 153) at doses of 1, 10 or 100 ng/ml each, separately or jointly with RU486. The effect of PCB 77 and 153 on oxytocin secretion was blocked by RU486, but it did not change the effect evoked by PCB126 in both granulosa and luteal cells. We assume that some PCB congeners can affect oxytocin secretion from granulosa and luteal cells acting via GCr.