Molecular identification of a novel prostaglandin‐specific organic anion transporter (OAT‐PG) that is colocalized with prostaglandin producing enzyme Cox‐2 in the distal tubular cells.

Abstract

Since Prostaglandins (PGs) are charged organic anions at physiological pH, PGs transport across the plasma membrane is a carrier-mediated process. In the kidney, especially at the distal tubules, prostaglandinE2 (PGE2) contributes to renal hemodynamics, renin release, and tubular sodium and water level regulation. In this study, we isolated a cDNA encoding a novel prostaglandin-specific transporter from mouse kidney. Because this transporter belongs to organic anion transporter (OAT) family (SLC22) structurally distinct from PGT (SLC0), we named it prostaglandin-specific organic anion transporter (OAT-PG). OAT-PG specifically mediated a transport of PGs, whereas other organic anions (para-aminohippurate, estrone sulfate, taurocholate), organic cations (TEA, choline), and zwitterion (carnitine) were not transported by OAT-PG. OAT-PG mRNA is expressed only in kidney. Immunohistochemical analysis showed that OAT-PG and cyclooxygenase-2 (cox-2) protein were colocalized at the renal distal tubular cells. We speculate OAT-PG and cox-2 would be functionally coupled in distal tubular cells for releasing PGE2 and contribute to renal physiological functions involving in PGE2 metabolism and signaling.