OBJECTIVE: To elucidate the role of platelet-derived growth factor (PDGF) in the pathophysiology of pregnancy-induced hypertension (PIH) in which the spiral arteries of the decidua demonstrate the atherosclerotic change. DESIGN AND METHODS: We determined serum levels of PDGF and PDGF expression in the decidua as well as serum levels of 17 beta-estradiol (E2) and progesterone (P4) both in normotensive cases and in PIH cases. Furthermore, we investigated whether sex steroid hormones could interact with PDGF in cultured vascular smooth muscle cells (SMC) by immunohistochemical staining for proliferating cell nuclear antigen. RESULTS: Serum PDGF levels were higher (P<0.01) but serum E2 levels were lower (P<0.01) in PIH cases compared with normotensive cases. There was no statistically significant difference between serum P4 levels in PIH cases and those in normotensive cases. Immunohistochemical staining for PDGF in SMC of spiral arteries was more prominent in PIH cases than in normotensive cases. The proliferative potential of cultured SMC was stimulated by PDGF, but inhibited by concomitant treatment with PDGF and E2. CONCLUSIONS: PDGF is suggested to play an important role in the pathophysiology of PIH through its stimulatory effect on vascular SMC proliferation which may elicit the atherosclerotic change in the spiral arteries of the placenta.