Turnover of collagen in the adult rat after denervation.

Unilateral denervation of the hind limb in a group of adult rats prelabeled with radioactive proline induced a significant turnover of collagen in tendons, ligaments, menisci, and bones. After two or three months of disuse, there were significant losses (15 to 29 per cent) of old collagen from the four structures studied. Dilution of the radioactivity of the old collagen with new collagen involved partial to complete replacement of 3 to 20 per cent. The incomplete replacement of destroyed collagen with new collagen resulted in a net decrease of collagen mass ranging from 5 to 14 per cent. A significant turnover of collagen in two-year-old rats that showed little loss in collagen mass means that the new collagen produced would have fewer cross-links and would probably be weaker than the old, mature collagen.