Molecular cloning and intrarenal localization of rat prostaglandin E2 receptor EP3 subtype.

A rat kidney cDNA library was screened with a mouse prostaglandin (PG) E2 receptor EP3 alpha subtype cDNA as a probe, and a 2.2-kilobase pair cDNA was isolated. The cDNA encodes 365 amino acids with 97.0% sequence identity to mouse EP3 alpha receptor. Specific binding of [3H]PGE2 was found in COS-7 cells transfected with the cDNA (Kd = 3.2nM) and was displaced with unlabeled prostaglandins in the order of PGE2 = PGE1 >> PGF2 alpha > PGD2. Thus, a cDNA for rat EP3 (rEP3) receptor was cloned. In situ hybridization revealed expression of rEP3 receptor principally in tubules of renal medulla. Consistent with this observation, the reverse transcription and polymerase chain reaction (RT-PCR) technique using dissected nephron segments showed the receptor expression specifically in medullary thick ascending limbs of Henle's loop (mTAL), cortical TAL (cTAL), cortical collecting ducts (CCD) and inner medullary collecting ducts (IMCD), indicating a possible diuretic and natriuretic role of rEP3 receptor at the distal nephron segments.