Abstract： The present study aimed to investigate the role of platelet-activating factor (PAF) in progesterone synthesis and vascularendothelial growth factor (VEGF) expression in rat luteal cells. Immature (25-28 days old) female Sprague-Dawley rats were injectedsubcutaneously with 50 IU pregnant mare serum gonadotrophin (PMSG), and 25 IU human chorionic gonadotrophin (hCG) 48 h later,to induce folliclular development and luteum formation. On day 6 after hCG administration (the day of hCG administration was thefirst day), the rats were killed by guillotine and the ovarian luteal cells were collected. After incubation for 24 h, luteal cells wereincubated without or with different doses (0.1 μg/mL, 1 μg/mL, 10 μg/mL) of PAF at 37 ℃ (5% CO2) for 24 h, and then progesteroneconcentration was evaluated by radioimmunoassay (RIA); apoptotic rate and VEGF rnRNA expression in luteal cells were assessed byflow cytometry and RT-PCR, respectively. The results showed that PAF promoted progesterone production, with a maximal effect at 1μg/mL (P<0.05); PAF increased apoptotic rate but not in a dose-dependent manner, and 10 μg/mL PAF enhanced apoptotic rate signifi-cantly (P<0.05); furthermore, PAF stimulated VEGF mRNA expression in luteal cells, especially at 1 μg/mL (P<0.01). It is suggested thatPAF regulates progesterone synthesis and VEGF mRNA expression in luteal cells to mediate corpus luteum formation in rat ovary.