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.