The migration and proliferation of vascular smooth muscle cells (SMC) into the neointima are important early events in the development of atherosclerosis and post-angioplasty restenosis. The stimulation of SMC migration by platelet derived growth factor (PDGF) involves the induction of protein kinase C activity. Using immunoblot techniques, we demonstrated that rat aortic SMC express a pattern of PKC isoforms which includes PKC-alpha, delta, epsilon, zeta and eta. Upon exposure to PDGF-BB, a fraction of PKC-delta was rapidly translocated from the cytosol to the post-nuclear particulate fraction at 15 seconds and reached an apparent maximum at 30 minutes. In contrast, PKC-alpha and zeta were not translocated by PDGF-BB, TGF-beta 1, which inhibits PDGF-induced DNA synthesis and chemotaxis, reduced the immunoreactive levels of PKC-delta and blocked the PDGF-induced translocation of PKC-delta to the particulate fraction. This suggests that the activation of PKC-delta by translocation to the particulate fraction may play an important role in the control of vascular smooth muscle cell migration by PDGF and TGF-beta 1.