Circulating factors that modify lung cell DNA synthesis following exposure to inhaled oxidants. I. Effect of serum and lavage on lung fibroblasts following exposure of adult rats to 1 ppm ozone

Adult rats were exposed to 1 ppm (1.96 mg/m3) ozone or air for 2 wk. Animals were sacrificed at 3, 5, 7, or 14 d after the onset of exposure, and samples of plasma and lung lavage were obtained. Heat-inactivated plasma, from animals exposed to ozone for 7 or 14 d, significantly increased DNA synthesis by lung fibroblasts compared with plasma from air-exposed animals. Fractionation of plasma and lavage samples indicated that the factor responsible had an isoelectric point of 6.45-6.75 and a molecular weight of 32 ± 2 kDa. This factor has a dose-dependent effect on lung fibroblast DNA synthesis in culture, but no significant effect on cultured pneumocyte DNA synthesis. The factor is detectable within 72 h of exposure, and may hold some promise as a marker of early oxidant lung injury.