Platelet-activating factor (PAF) and its receptors are involved in inflammatory-like processes of the uterus associated with increased vascular permeability. PAF is supposed to be influenced by ovarian steroid hormones. The present study was undertaken to examine whether progesterone (P(4)), estradiol (E(2)) or PAF influence the PAF receptor gene expression in perfused endometrial explants derived from ovariectomized bovine. Furthermore, we identified the cell types in which the PAF receptor gene and protein are expressed. In endometrial explants, applications of 10 nM P(4) or 10nM P(4) plus 10 nM E(2) for 24 h induced elevated transcript levels of PAF receptor in comparison to the controls or after treatment with 1 nM E(2). When explants were administered 10 nM E(2), a slight decrease in the transcript level was recorded. After treatment of explants with PAF, no significant changes in PAF receptor mRNA expression was observed compared to the control group. We demonstrate that PAF receptor immunoreactivity and mRNA are detected mainly in the luminal epithelium, epithelial cells of the superficial glands and to a lesser degree in stroma. Levels of PAF receptor mRNA in bovine endometrial explants were correlated with PAF receptor protein localization assessed by immunohistochemistry. The regulation of PAF receptor by progesterone in bovine endometrial explants suggests that PAF is involved in the physiological process of reproduction.