Biochemical quantitation and histochemical localization of cathepsin B, dipeptidyl peptidases I and II, and acid phosphatase in pulmonary granulomatosis and fibrosis in rats.

The purpose of this study was to quantitate biochemically and to localize histochemically the proteases cathepsin B (Cath B), dipeptidyl peptidase I (DPP I), and dipeptidyl peptidase II (DPP II) in experimental pulmonary granulomatosis and fibrosis. These were compared to the prototypical lysosomal hydrolase acid phosphatase (AP). Granulomatosis was induced by the intravenous injection of complete Freund's adjuvant (CFA, 0.2 ml) and fibrosis was induced by the intratracheal instillation of bleomycin sulfate (1 unit) in rats (Wistar, 200 g). Total Cath B, DPP I, and AP activities were markedly elevated over control values five days following both treatments when expressed as activity per lung or as specific activity per milligram protein or milligram DNA. By 14 and 28 days, total activity was elevated for all three enzymes, and activity per milligram DNA remained elevated for Cath B following both treatments and for DPP I 28 days following CFA treatment. Total lung activity of DPP II was significantly elevated at 28 days for both treatments. Histochemical staining indicated that these changes are due, in part, to the influx of inflammatory monocytes and their maturation to macrophages. This study provides a basis for examining the role of these proteases in connective tissue matrix injury during inflammatory processes in the lungs.