EPIDERMAL GROWTH FATTER-LIKE ACTIVITY IN BRONCHOALVEOLAR LAVAGE FLUIDIN EXPERIMENTAL SILICOSIS

We investigated whether development of pulmonary fibrosis following in halational exposure of mice to silica (quartz) dust was accompanied by enhanced secretion of activity resembling epidermal growth factor (EG F). Mitogenic activity for pulmonary fibroblasts was assessed in bronc hoalveolar lavage fluid (BALF) using a serum-free bioassay. Activity i n BALF from mice exposed to nonfibrogenic titanium dioxide dust was co mparable to that in BALF from normal animals. In contrast, mitogenic a ctivity was significantly increased at 6 and 12 weeks after inhalation of silica particles, coinciding with the appearance of collagenised l esions in the lung. BALF from mice exposed to silica 6 weeks previousl y had significantly higher concentrations of growth factor(s) able to bind to EGF receptors on pulmonary fibroblasts. In parallel, macrophag es within inflammatory lesions in the airspaces acquired immunoreactiv ity for EGF. The presence of an increased concentration of EGF-like gr owth factor(s) in BALF might constitute a marker of particle-induced p ulmonary fibrosis.