Phytoestrogens reduce the effect of polychlorinated biphenyls on the contractility of bovine myometrium in vitro

Proper regulation of uterine contractility, both spontaneous and oxytocin (OT)-amplified, is essential for successful fertilization and maintenance of gestation. Previously, we showed that polychlorinated biphenyls (PCBs), regarded as environmental pollutants, contributed to the increase in contractions of cyclic bovine uterus. In this paper, we hypothesized that phytoestrogens, plant-derived components, counteract the disruptive effects of PCBs. Therefore, we examined the in vitro effect (24–72 h) of coumestrol, daidzein, and genistein (10–6, 10–5M each) on spontaneous and OT-stimulated (10–7M) myometrial strips contractions. Moreover, the effect (48 h) of coumestrol (10–6M) or daidzein (10–5M), jointly with PCBs (77, 100 ng/ml; 126, 153, 10 ng/ml), on myometrial contractions was registered. The myometrium was the most relaxed (P < 0.05) when treated with coumestrol, while the force of myometrial spontaneous contractions increased the most (P < 0.05) when treated with daidzein. Daidzein (10–5M) also effectively increased the OT-stimulated force of contractions (P < 0.01). All phytoestrogens used affected the frequency and amplitude of myometrial contractions, though less markedly. Furthermore, coumestrol or daidzein reduced (P < 0.05) the spontaneous and OT-stimulated force of myometrial contractions, evoked by PCBs. Data suggest the effect of PCBs on myometrial contractility can be markedly reduced by some phytoestrogens.