Prostaglandins (PG) mediate IL-1β regulation of several interleukin mRNAs in progenitor Leydig cells. PGE_2 and PGF_2α potently reverse indomethacin (INDO; a cyclooxygenase inhibitor) inhibition of IL-1β autoinduction. IL-1β increases PGE_2 and PGF_2α production. To determine the PG receptors involved in this regulation, this study established by RT-PCR and Western analyses which specific receptors for PGE_2 (EP receptors) and PGF_2α (FP receptors) are expressed in progenitors. Pharmacological characterization of receptors involved in PGE_2 and PGF_2α regulation of IL-1β mRNA levels was ascertained using real-time PCR analyses. FP, EP_1, EP_2, and EP_4 receptor mRNAs and proteins, and an EP_3 receptor subtype were detected. IL-1β treatment (24-h) significantly decreased EP_1 receptor levels; INDO abrogated this down-regulation. FP, EP_2, and EP_4 receptor levels increased after IL-1β and IL-1β + INDO. A selective FP agonist, cloprostenol (0.1 µM), and PGF_2α (10 µM) had similar effects on IL-1β mRNA levels in progenitors treated with IL-1β + INDO. None of the EP_2/EP_4 agonists [butaprost, misoprostol, or 11-deoxy PGE_1 (10 µM)] affected IL-1β mRNA levels. In contrast, EP_1/EP_3 agonists (17-phenyltrinor PGE_2 and sulprostone) increased IL-1β mRNAs in a dose-dependent manner. EP_2 receptor subtype-selective antagonist, SC-51322, blocked IL-1β-induced and [IL-1β+ INDO + 17-phenyl trinor PGE_2]-induced increases in IL-1β mRNAs. Taken together, our data demonstrate that FP and EP_1 receptors mediate PGF_2α and PGE_2 induction of progenitor IL-1β expression.