Lung collagenase inhibitors and spontaneous and latent collagenase activity in idiopathic pulmonary fibrosis and hypersensitivity pneumonitis.

In order to analyze the mechanisms involved in the decreased collagenolytic activity previously observed in interstitial lung fibrosis, we studied the inhibitory collagenase activity and the latent activable collagenase in lung samples from five patients with IPF, six with HP, and three control subjects. Our results showed that in both diseases, the inhibitor levels were significantly higher than in control subjects. Findings suggest that in IPF low amounts of collagenase plus excessive enzyme-inhibitors may be operating to decrease collagen catabolism. In contrast, HP lungs seem to contain adequate amounts of the enzyme but higher levels of inhibitors play a role in the abnormal degradation observed in some patients.