This study investigated the expression of genes involved in prostaglandin production and secretion of prostaglandin F2alpha and E2 in the endometrium of sexually active cats at different stages of the estrous cycle. Sex steroid treatment increased PGE2 secretion and expression of the PGE2 synthase gene at the follicular and luteal phases. Progesterone alone enhanced PGE2 secretion at the follicular and late luteal phase, while combined treatment with estrogen increased PGE2 output at the follicular and mid-luteal phase. The findings support that PGF2alpha plays a minor role in regulating the estrous cycle in cats, while increased PGE2 secretion and upregulation of PGE