Inhibitors of collagenase in ligaments and tendons of rabbits immobilized for 4 weeks.

Our laboratories have previously measured the capacity for collagenase production by normal and immobilized rabbit periarticular connective tissues (PCT), i.e., anterior cruciate ligaments (ACL), medial collateral ligament (MCL) and patellar tendon (PT). Rabbit limbs were immobilized for 4 weeks and then the tissues were cultured for 4 days. Collagenase and inhibitor (TIMP) were measured in the medium. Collagenase activity was significantly decreased in the medium from all experimental tissues, relative to the levels in contralateral control tissues. On the other hand there was no significant change in inhibitor levels in the three experimental tissues. These results support the idea that collagenase is decreased due to decreased enzyme expression and not to increased inhibitor production.