Endocrine Abstracts

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants. Two industrial PCB mixtures, Aroclors 1221 and 1254 have been suggested to have estrogenic and anti-estrogenic properties, respectively. We have examined whether these PCB mixtures modulated bone formation and resorption in intact and ovariectomized (ovx) rat models. Twentyfour adult female rats were divided into three groups subcutaneously receiving 4% DMSO (Control), Aroclor 1221 (10 mg/kg) and Aroclor 1254 (10 mg/kg). These compounds were injected to the animals for a period of six weeks at two daily intervals. In the second model, rats (n=24) were ovx and allowed to recover for a period of at least three weeks. Control group received vehicle (4% DMSO) alone. Remaining rats were divided into two groups and injected (sc) with Aroclor 1221 (10 mg/kg/0.5 ml) and Aroclor 1254 (10 mg/kg 0.5 ml) for five weeks. At the end, all animals were decapitated. Serum alkaline phosphatase (ALP) and osteocalcin levels were determined by autoanalyzer and immunoradiometric method, respectively. Urinary deoxypyridinoline (DPD, a bone absorption marker) was measured by ELISA. Lumbar vertebrae (L2) of all animals were dissected out and processed for light microscopy. Ovx significantly increased urinary DPD excretion (p<0.01) compared to intact control values. Administration of Aroclors 1221 and 1254 had no significant effects in intact rats, however, they significantly reduced (p<0.05) and increased (p<0.001) urinary DPD levels in ovx rats, respectively. Neither estrogenic nor anti-estrogenic PCB mixtures significantly changed serum osteocalcin and ALP levels in intact or ovx rats (except Aroclor 1221 increased ALP in intact model, p<0.01). Treatment with Aroclor 1221 reversed the adverse effects of ovariectomy on L2 histology. However, Aroclor 1254 produced necrotic areas in vertebral bone, and this effect was expanded in ovx animals. Our findings indicate that both Aroclor compounds interfere with bone turnover mechanisms, particularly in ovx rats.