Prostanoid signaling, localization, and expression of IP receptors in rat thick ascending limb cells

It is widely held that only one prostacyclin (IP) receptor exists that can couple to guanine stimulatory nucleotide binding proteins (G(s)) leading to activation of adenyl cyclase. Although IP receptor mRNA is expressed in va scular arterial smooth muscle cells and platelets, with lower level express ion in mature thymocytes, splenic lymphocytes, and megakaryocytes, there is no molecular evidence for IP receptor expression in renal epithelial cells . The purpose of the present study was to obtain molecular evidence for the expression and localization of the IP receptor and to study the signaling pathways of IP receptor in rat medullary thick ascending limb (MTAL). Bioch emical studies showed that IP prostanoids do not increase cAMP in rat MTAL. However, in the presence of vasopressin, inhibition of cAMP formation by p rostacyclin (PGI(2)) analogs is pertussis toxin sensitive and does not acti vate protein kinase C. In situ hybridization studies localized IP receptor mRNA expression to MTAL in the rat kidney outer medulla. The results of RT- PCR of freshly isolated RNA from MTAL, with primers specific for the mouse IP receptor cDNA, produced an amplification product of the correct predicte d size that contained an expected Nco I endonuclease restriction site. We c onclude that rat renal epithelial cells express the IP receptor, coupled to inhibition of cAMP production.