Effects of acute exposure to PCBs 126 and 153 on anterior pituitary and thyroid hormones and FSH isoforms in adult Sprague Dawley male rats

3,3',4,4',5-Pentachlorobiphenyl (PCB 126) and 2,2',4,4',5,5'-hexachlorobiph enyl (PCB 153) were administered to adult male rats in order to identify se nsitive indicators of endocrine disruption. We tested the hypothesis that P CB exposure modifies follicle-stimulating hormone (FSH) pituitary isoforms, as well as the pituitary and serum concentrations of FSH, luteinizing horm one (LH), growth hormone, prolactin, and thyroid-stimulating hormone (TSH). Effects on serum levels of thyroxine (T-4) and testosterone (T), and prost ate androgen receptor content, were also tested. In one experiment, 5 group s of 8 rats each received two ip injections, one day apart, of either corn oil or 6.25, 25, 100 or 400 mu g/kg/day of PCB 126. Decreases (p < 0.05) in the serum concentrations of T4 and LH started at doses of 25 and 100 mu g/ kg/day, respectively. Serum FSH concentrations were reduced (p = 0.07) in t he highest dose group. In contrast, pituitary content of FSH and LH increas ed with PCB-126 doses (p = 0.004, p = 0.002, respectively). Despite changes in reproductive hormones, PCB-126 had no effect on the androgen receptor c ontent of the prostate. The effect of PCB-126 was tested in the hemicastrat ed rat, and suggested adverse effects on testosterone secretion. To test th e effects of PCB exposure on FSH pituitary isoforms, 4 groups of 10 male ra ts received two ip injections, one day apart, of either corn oil, PCB 153 ( 25 mg/kg/day), estradiol-17 beta (E2; 20 mu g/kg/day), or PCB 126 (0.1 mg/k g/day). Serum T4 levels were higher (p < 0.01) in the E2 and PCB 153 groups , and slightly reduced in the PCB 126-treated groups, compared to controls. Simultaneous purification of pituitary FSH and TSH isoforms was performed by HPLC, using two chromatofocusing columns in series. In contrast to TSH i soforms, the distribution of FSH isoforms over the chromatography run diffe red slightly between treatment groups; the amounts of FSH isoform eluted du ring the pH gradient were lower (p < 0.05) in E2 and PCB 153-treated rats t han in control or PCB 126-treated rats. The similarity between the effects of E2 and PCB 153 on T4 and FSH isoforms supports the contention that PCB 1 53 possesses estrogenic properties. Serum LH and T4 concentrations were the most sensitive and practical endocrine indicators of PCBs 126 and 153 expo sure in male rats.