Molecular cloning and spatio-temporal expression of the prostaglandin transporter: A basis for the action of prostaglandins in the bovine reproductive system

Prostaglandins (PGs) play important roles in mammalian reproductive function through autocrine, paracrine, and endocrine actions. However, they predominate as charged anions and diffuse poorly across the plasma membrane. Recently, a PG transporter (PGT) has been found to mediate PG transport across cell membranes. In ruminants, endometrial PGs are transported by a vascular pathway to the ovary to regress or rescue the corpus luteum. There is no report on the role of PGT in the reproductive functions of any species. We have cloned and characterized the bovine PGT (bPGT) that transports different PGs in the following affinity order: PGE2 = PGF(2alpha) greater than or equal to PGD(2) much greater than arachidonate. bPGT mRNA and protein are expressed in endometrium, myometrium, and the utero-ovarian plexus (UOP) during the estrous cycle. The level of bPGT expression is higher in endometrium and UOP on the side of corpus luteum between days 13 and 18 of the estrous cycle. bPGT protein is localized in endometrial stroma, luminal epithelial cells, myometrial smooth muscle cells, and vascular smooth muscle cells of uterine vein and artery. In UOP, bPGT is selectively expressed in vascular smooth muscle cells of uterine vein and ovarian artery. Spatio-temporal expression of bPGT in uterine tissues and UOP supports a significant role of bPGT in cellular and compartmental transport of PGs to mediate the endocrine action at the time of luteolysis or establishment of pregnancy in bovine. This study describes and proposes a role of PGT in the regulation of reproductive processes.