Effect of polychlorinated biphenyls bone tissue, parathyroid hormone, calcitonin, bone turnover parameters at adult female rats

2. ABSTRACT Polychlorinated biphenyls (PCBs) were produced for industrial purposes and banned in several countries in the world when they were determined to be persistent pollutants in the environment. However, many PCB-containing industrial products and equipments are still in use and thus pose a threat to the environment and human health. They tend to bio-accumulate both in the environment and living organisms due to their lipophilic features and chemical stability. Several effects of PCBs including toxicity, carcinogenicity, immunsuppression and endocrine disruption have been investigated. However, there is very limited data on their actions on the bone tissue. We have examined the effects of two industrial PCB mixtures, Aroclors 1221 (A 1221) and 1254 (A1254) and estradiol on bone turnover markers deoxypyridinolin (DPD), osteocalcin, alkaline phosphatase (ALP), calcitonin, parathyroid hormone (PTH), serum Ca and inorganic phosphate levels; in addition on bone mineral density (BMD) and histology in intact and ovariectomized (OVX) rat models. Adult female Wistar rats (200-220g) were used in this study. In the first experimental model, a total of 33 animals were divided into four groups. They were subcutaneously injected with DMSO (4%), A1221 (10mg/kg), A1254 (10mg/kg) and östradiol (30p,g/kg) at two daily intervals for a period of six weeks. In the second model, 33 rats were bilaterally OVX and divided into four groups. Sham OVX rats in the first group received vehicle alone, and the others A 1221, A1254 and estradiol, respectively, at two daily intervals for 34 days. At the end, all animals were decapitated. Serum PTH, calcitonin and osteocalcin levels weredetermined by immunoradiometric method. Urinary DPD was measured by ELISA and serum ALP, Ca and inorganic phosphate concentrations by autoanalyzer using Olympus kits. Lumbar vertebrae (L2) of all animals were dissected out and processed for light microscopy. BMD of femur and tibia were determined by bone densitometry. Administration of A1221 or 1254 to intact rats caused no significant changes in urinary DPD and serum osteocalcin, calcitonin, PTH, inorganic phosphate levels and femur and tibia BMD values, but increases in the serum levels of Ca and ALP were observed. Oestradiol injection resulted in significant reductions in DPD, osteokalsin and ALP levels and elevations in calcitonin, PTH, Ca and tibia BMD values. In the sham OVX group, DPD, osteocalcin and calcitonin levels were significantly increased and Ca concentrations decreased compared to the intact control group. Administration of A1221 to OVX animals caused significant reduction in urinary DPD and elevation in serum inorganic phosphate and femur BMD. However, it had no significant effect on serum ostocalcin, calcitonin, PTH, Ca, ALP levels and tibia BMD. A1254 administration significantly increased urinary DPD levels and also caused important changes in the L2 vertebral bone histology. Injection of estradiol to OVX rats resulted in significant reductions in DPD, osteocalcin and calcitonin levels, and increases in Ca, inorganic phosphate, femur and tibia BMD values. Our findings indicate that both Aroclor compounds may interfere with bone formation and resorption mechanisms. In particular, A1254 increased the loss of bone organic matrix in the absence of estrogen. Keywords: PCB, DPD, osteocalcin, PTH, calcitonin, estradiol