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 EP_3α 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 EP_3α 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 >> PGF_2α > 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.