COLLAGEN TYPE-I OF RAT CORTICAL AND TRABECULAR BONE DIFFERS IN THE EXTENT OF POSTTRANSLATIONAL MODIFICATIONS

This study sought to evaluate whether the architecture of the matrix o f cortical and trabecular bone is exactly the same. For this purpose w e analyzed the extent of some posttranslational modifications of type I collagen, which is the major component of bone matrix. Ten female an d 10 male 100-day-old rats were sacrificed and the content of hydroxyl ysine, glycosylated hydroxylysine, and pyridinium cross-links of colla gen from cortical and trabecular bone was determined. The amount of ea ch compound was expressed as a molar ratio with hydroxyproline. The co llagen posttranslational modification pattern appears to be the same i n both sexes but with a higher extent of differences in females compar ed with males. Comparing cortical and trabecular bone, the former cont ains a higher amount of hydroxylysine residues whereas in the latter, glycosylation of hydroxylysine is higher and pyridinium cross-link con centration is lower. Moreover, an inverse linear relationship between glycosylated hydroxylysine and pyridinium crosslinks concentration was established, both for female (r = - 0.455, P = 0.04) and male rats (r = - 0.426; P = 0.06). This paper discusses what these findings may me an in functional terms.