Dose-dependent effects in the subacute response of the rat lung to quartz. II. Protease activities and levels of soluble hydroxyproline in lung lavage.

The response of the rat lung to a range of doses of quartz at 50 and 100 days after its administration by intratracheal instillation has been assessed by bronchopulmonary lavage. The effects on the levels of protein and hydroxyproline and on the PZ peptidase and collagenolytic activities of lavage fluid supernatants are described and an assessment of the hydroxyproline content of recovered cells is made. In addition, assays for PZ peptidase and collagenase activity were carried out on polymorph enriched fractions and on samples obtained from short-term culture of recovered macrophages. Both protein and hydroxyproline measurements did show dependence on the amount of quartz instilled and the time after its administration. Measurements of PZ peptidase and collagenase activities suggest that the polymorphonuclear leukocytes, not the macrophages, are the major source of these degradative enzymes. The relevance of these findings with regard to the importance of the PMN in quartz-induced fibrosis, is discussed.