IN-SITU HYBRIDIZATION AND LOCALIZATION OF MESSENGER-RNA FOR THE RABBIT PROSTAGLANDIN EP(3) RECEPTOR

The physiological effects of PGE2 appear to be mediated by at least three different ''E-prostanoid'' receptors designated EP1, EP2, and EP3. These receptors are differentially activated by structural PGE analogs (such as misoprostol) and each couples to a different signal transduction mechanism. Studies demonstrating that inhibition of water absorption in the collecting duct is mediated by a G(i) coupled mechanism, suggests that an EP3 receptor is involved the renal effects of PGE2. We used in situ hybridization to determine the tissue distribution of the rabbit EP3 receptor. [Alpha-S-35] UTP labeled antisense RNA, comprising transmembrane domains IV through VII, was hybridized to tissue sections. Specific labeling of kidney, stomach and adrenal was observed. In the kidney, medullary thick ascending limb and cortical and medullary collecting ducts were intensely labeled, while no labeling of glomeruli, proximal tubules, or cortical thick ascending limbs was observed. The adrenal gland labeled exclusively in the medulla. In the stomach the gastric epithelial crypts were the predominant site of hybridization, without evidence of labeling of the smooth muscle. These results suggest an important role for the EP3 receptor in mediating PGE2 effects in these tissues.