Experiments were designed to determine how ovariectomy modulates mitogenic factors in platelets and how these factors affect proliferation of coronary arterial smooth muscle. Platelet-derived growth factors (PDGF(AB) and PDGF(BB)), transforming growth factors (TGF-beta(1) and TGF-beta(2)), and vascular endothelial growth factor (VEGF(165)) were quantified in platelet lysates and platelet-poor plasma from adult gonadally intact and ovariectomized female pigs by ELISA. Proliferation of cultured coronary arterial smooth muscle cells (SMCs) from both groups of pigs was determined in response to autologous or heterologous platelet lysates. Platelet concentrations of PDGF(BB), but not PDGF(AB), TGF-beta(1), and TGF-beta(2), increased with ovariectomy. VEGF(165) was not detected in platelets from either group. Proliferation of SMCs from ovariectomized females was significantly greater on exposure to autologous or heterologous platelet lysates than proliferation of SMCs from intact females. These results indicate that ovariectomy increases concentrations of PDGF(BB) in platelets. Higher levels of PDGF(BB) in platelets in synergy with other platelet-derived products could contribute to increased proliferative arterial response to injury after ovariectomy.