Release of amino-terminal procollagen peptides in paraquat-induced acute pulmonary fibrosis.

Acute pulmonary fibrosis following intoxication with paraquat is characterized by increased collagen synthesis and deposition in the lungs. In the present study, a chronic lung lymph fistula preparation in sheep was used to investigate the changes in procollagen type III peptide level in the lung lymph in acute pulmonary distress associated with paraquat application. The procollagen type III peptide is supposed to be an indicator of the changing biosynthetic pattern of pulmonary collagen in lung fibrosis. All animals tested showed a progressive pulmonary distress following the application of paraquat characterized by increasing lymph flows and lymph protein flows which monitored the microvascular membrane damage. In parallel to these findings, procollagen peptide levels in the lymph fluid increased, even before manifest biochemically or histologically detectable pulmonary fibrosis occurred. The present results suggest that the release of procollagen type III peptides into lymph fluid is an early indicator of beginning fibrotic tissue disarrangement, even before completed pulmonary fibrosis can be detected by common tissue analysis.