Training affects the collagen framework of subchondral bone in foals

Subchondral bone provides structural support to the overlying articular car tilage and plays an important role in osteochondral diseases. There is grow ing insight that the mechanical features of bone are related to the biochem istry of the collagen network. In this study the effect of exercise on wate r calcium and the collagen network (total collagen, lysyl-hydroxylation, hy droxylysylpyridinoline, and lysylpyridinoline crosslinks) of subchondral bo ne at two differently loaded sites (site 1: intermittantly loaded; site 2: constantly loaded) is investigated in foals. Exercise influenced calcium content and levels of both types of crosslinks at site 1, but had no influence on site 2. There was no concomitant increas e in lysyl-hydroxylation level with the rise in crosslinks. Levels of lysyl -hydroxylation and lysylpyridinoline crosslinking were lower at site 1 than at site 2. It is concluded that exercise affects the post-translational mo difications of the collagen component of subchondral bone. Loading also app ears to play a role in site-related topographical differences. The lack of any relation between the sum of pyridinoline crosslinks and the amount of t riple helical hydroxylysine gives support to a recent hypothesis that lysyl -hydroxylation of the triple helix and the telopeptides are under seperate control. (C) 2001 Harcourt Publishers Ltd.