Endothelial cells subjected to cell injury are capable of producing platelet-derived growth factor (PDGF), a mitogen for the stimulation of fibroblast and smooth muscle cell proliferation. Cultured bovine pulmonary artery endothelial cells were exposed to low concentrations of H2O2 for 30 min. Total cell RNA was isolated and subjected to Northern analysis with use of a v-sis PDGF cDNA probe. Results demonstrate a fourfold increase in cell PDGF mRNA immediately after exposure of bovine pulmonary artery endothelial cells to 50 microM H2O2. Evidence of expression of PDGF was sought in samples of cell supernatant collected 48 h after exposure. No evidence of PDGF activity or PDGF antigen could be demonstrated in those supernatants. Although the biologic activities of PDGF suggest that PDGF production by endothelial cells may contribute to the pulmonary pathology associated with acute lung injury, our results suggest that posttranscriptional events may prevent expression of PDGF under the experimental conditions of this investigation.