Short-term exposure to dioxin impairs bone tissue in male rats

Chronic and sub-chronic studies in rats have previously shown that dioxin-like compounds impair the bone tissue homeostasis. In the present study, tibiae and serum were analyzed to study possible effects of short term dioxin exposure on rats. Two month old (ca. 200g) male rats were injected with 50microg 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) kg(-1) bw and tibiae were excised 5d following the exposure. Bone composition, dimensions and strength were analyzed by pQCT and three-point bending test on tibiae. In addition, detailed bone composition was analyzed by optical emission spectroscopy (ICP-OES) and Fourier transform infrared spectrometry (FTIR). Analysis of the serum bone biomarkers procollagen type-I N-terminal propeptide (PINP) and carboxyterminal cross linking teleopeptide (CTX) were also performed. pQCT-results showed alterations in the metaphysis, with a significant decrease in trabecular bone cross-sectional area (-19%, p<0.05) and a significant increase in total bone mineral density (+7%, p<0.05) in TCDD-exposed rats. Analyses of the bones by ICP-OES and FTIR showed that bones from exposed rats had a higher relative proportion of crystalline phosphate (+13% for a1080 and +11% for a1113, p<0.05) and lower acid phosphate content (-22% for a1145, p<0.05), resembling the composition of more mature bones. Serum analysis showed that the bone formation marker PINP was decreased (-37%, p<0.05) and that the bone resorption marker CTX was increased (+14%, p<0.05) indicating a net loss of bone tissue. In conclusion, 5d of exposure to TCDD was sufficient to negatively affect bone tissue in male rats.