Collagenolytic cathepsin B and L activity in experimental fibrotic liver and human liver.

To clarify the role of individual collagenolytic cathepsin in hepatic collagen degradation, cathepsin B and L activities were determined in normal and CCl4-induced fibrotic liver, together with non-collagenolytic cathepsin H. Cathepsin B and L activities increased 1.9- and 2.0- fold, respectively, in the fibrotic liver as compared with the normal liver, and were significantly correlated with hepatic hydroxyproline levels. By contrast, cathepsin H activity was not altered in fibrotic rats. Similar results were also obtained from autopsied human livers. These results suggest that cathepsin B and L are similarly induced by hepatic collagen levels and are implicated in degrading collagens, especially soluble collagen.