Bone tissue composition, dimensions and strength in female rats given an increased dietary level of vitamin A or exposed to 3,3 ',4,4 ',5-pentachlorobiphenyl (PCB126) alone or in combination with vitamin C

In previous studies we have described structural and functional changes in rat bone tissue caused by 3,3',4,4',5-pentachlorobiphenyl (PCB126). Some of the effects caused by PCB126 resemble those found in vitamin C-deficient r ats, as well as those found in rats with a high dietary intake of vitamin A . The present investigation was designed to determine if these PCB 126-indu ced changes could be inhibited by addition of vitamin C to the drinking wat er and if they could be evoked by vitamin A administration. Five groups of female rats were used in this study, which lasted for 12 weeks. Three: of t he groups were exposed to PCB126 (total dose 320 mug/kg, bw), either alone or in combination with vitamin C added to the drinking water (1 and 10 g/l, respectively). One group was given feed with increased level of vitamin A (600 000 U/kg pellet) and the fifth group served as controls. Using periphe ral quantitative computed tomography (pQCT), it was found that PCB126 incre ased trabecular density and cortical thickness, but reduced the trabecular area. Furthermore, maximum torque and stiffness of the humerus during torsi onal testing and serum osteocalcin levels were reduced by PCB126. OF the PC B126 induced effects observed, addition of vitamin C only inhibited the red uction of serum osteocalcin. Like PCB126 vitamin A supplementation increase d the inorganic content and the bone density and also reduced the trabecula r area and polar moment of inertia but did not increase the cortical thickn ess or reduce maximum torque, stiffness or serum osteocalcin level. Apparen tly. the effects induced by PCB126 are not mediated either via decreased vi tamin C level or increased vitamin A level. (C) 2000 Elsevier Science Irela nd Ltd. All rights reserved.