Effects of the antiestrogenic environmental pollutant 3,3 ',4,4 ',5-pentachlorobiphenyl (PCB #126) in rat bone and uterus: Diverging effects in ovariectomized and intact animals

The purpose of this study was to compare effects on rat bone and uterus of estrogen depletion and exposure to the coplanar PCB-congener 3,3',4,4',5-pe ntachlorobiphenyl (PCB #126) which exhibits anti-estrogenic properties. Hal f of the rats were ovariectomized (n = 20) and the other half were sham-ope rated. Ten of the ovariectomized rats and ten of the sham operated were exp osed to PCB #126 (ip injections) for 3 months (total dose: 384 mu g/kg body wt). The remaining control rats were injected with corn oil (vehicle). The rats were killed and the tibiae and uteri were dissected. The left tibia w as used for measurements of weight, length, and bone mineral density and th e right for histomorphometrical analysis. The uteri were analyzed with resp ect to estrogen receptor content. PCB #126 exposure did not affect bone min eral density or trabecular bone volume of tibia in sham-operated rats. In o variectomized rats PCB #126 exposure resulted in a decreased length and an increased bone mineral density of tibia. An obvious PCB #126 induced increa se in osteoid surface was observed in sham-operated rats. The cortical thic kness and the organic content of the tibia were also increased in these rat s. In estrogen deprived tissue like the uteri of ovariectomized rats, PCB # 126 showed weak estrogen agonistic activity. The observed effects of PCB #1 26 on bone and uterine tissues differed between ovariectomized and sham-ope rated rats. (C) 1999 Academic Press.