Change of bone tissue composition and impaired bone strength in rats exposed to 3,3 ',4,4 ',5-pentachlorobiphenyl (PCB126)

The aim of this study was to compare effects of estrogen depletion (ovariec tomy) and exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB126) on bone stre ngth and bone tissue composition in the rat. Half of the rats were ovariect omized (n = 20) and the remainder were sham-operated. Ten of the ovariectom ized rats and ten of the sham operated were exposed to PCB126 (ip injection s) for 3 months (total dose, 384 mu g/kg bodyweight), while those remaining received the vehicle. The humerus and femur were used for analysis of tors ional strength and biochemical studies, respectively. Both sham-operated an d ovariectomized animals showed a significantly shorter bone length, lower water content and a decreased torsional stiffness when exposed to PCB126. S ham-operated rats exposed to PCB126 had lower maximum torque when compared with sham operated controls. The PCB126-exposed rats also exhibited a signi ficantly lower collagen concentration, but showed a higher pyridinoline con centration of cortical bone. PCB126 exposure decreased the hepatic level of vitamin A but increased vitamin A levels in serum and kidneys. Ovariectomy per se increased bone length and organic content and decreased the inorgan ic content significantly, but did not affect any of the tested biomechanica l parameters. In conclusion, this study showed that the common environmenta l pollutant PCB126 impaired bone strength and altered bone composition. It is hypothesized that these effects might partly be explained by PCB-induced retinoid disturbances. (C) 2000 Elsevier Science Ireland Ltd. All rights r eserved.