Sex steroids, i.e. progesterone (P4) and 17β-estradiol (E2), fluctuate during the feline estrous cycle and their alterations correspond to many events in cat reproduction. In order to investigate possible effects of sex steroids on prostaglandin (PG) secretion in the cultured endometrial cells, mRNA expressions coding for PG-endoperoxide synthase (PTGS2) in the epithelial and stromal cells harvested with sex steroids were studied by RT-PCR. The effects of ovarian steroids on PG secretion in the epithelial and stromal cells were also investigated. E2 at a dose 10-7M significantly increased prostaglandin F2α (PGF2α) secretion in the epithelial cells (P<0.01). PGF2α production was intensified by the treatment in combination with both steroids (P<0.001). P4 at any dose alone had no effect on PGF2α secretion in the epithelial cells, whereas at a dose 10-5M enhanced prostaglandin E2 (PGE2) production (P<0.05). The ovarian steroids stimulated both PGF2α and PGE2 in the epithelial cells of the feline endometrium via an E2 receptor (ESR1)- and P4 receptor (PGR)-dependent genomic-pathway. In contrast to the epithelial cells, neither P4 nor E2 affected PG secretion in the stromal cells. PTGS2 mRNA expression was not affected by ovarian steroids in either cell types. The overall results suggest that PG secretion is regulated by P4 and E2 and this effect is not due to changes in PTGS2 mRNA expression.