Estrogenic and antiestrogenic actions of PCBs in the female rat: in vitro and in vivo studies.

A series of studies were performed to examine the effects of various PCB congeners [3,4,3',4'-TCB (PCB77), 2,5,2',5'-TCB (PCB52), 4' OH-2,4,6-TCB (OHPCB)] and a complex PCB mixture (Aroclor 1242; A1242) on the weights and patterns of cell proliferation of immature rat uteri in vivo and the effects of A1242 on gonadotropin release by dispersed anterior pituitary cells in vitro. Immature (20-day) rats were treated ip with corn oil (vehicle), PCBs, or 17 beta-estradiol (E2) once or daily for two consecutive days. Except for PCB77, all PCBs and E2 produced significant increases in uterine weights (P < 0.01) and increases in uterine 3H-thymidine labeling. PCB77 attenuated (P < 0.01) the increase in uterine weight due to either A1242 or E2 treatment. Cultured anterior pituitary cells exposed to varying concentrations of A1242 (0.1 to 50 ppm) exhibited enhanced gonadotropin responses to gonadotropin-releasing hormone (GnRH) similar to that of E2. These results demonstrate that PCBs can produce either estrogenic or antiestrogenic effects.