Using an injury model of the rat carotid artery and aorta, we have determined the time course of expression for PDGF ligands and receptors in endothelium by in situ hybridization and immunostaining. Platelet-derived growth factor (PDGF)-A and-B chains-were expressed in endothelial cells at the wound edge, but no expression was detectable in uninjured endothelium. PDGF-alpha receptor was expressed in a similar pattern as PDGF-A chain whereas expression of PDGF-beta receptor was not detected at any time. Expression of PDGF-B chain did not correlate with endothelial cell replication and a neutralizing antibody against PDGF-B had no effect on endothelial regrowth in the denuded aorta. Intimal smooth muscle cells are known to express PDGF-beta receptors and could thus be stimulated to migrate in response to PDGF-B from endothelial cells.