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 th ree different ''E-prostanoid'' receptors designated EP1, EP2, and EP3. These receptors are differentially activated by structural PGE analog s (such as misoprostol) and each couples to a different signal transdu ction mechanism. Studies demonstrating that inhibition of water absorp tion in the collecting duct is mediated by a G(i) coupled mechanism, s uggests that an EP3 receptor is involved the renal effects of PGE2. We used in situ hybridization to determine the tissue distribution of th e rabbit EP3 receptor. [Alpha-S-35] UTP labeled antisense RNA, compris ing transmembrane domains IV through VII, was hybridized to tissue sec tions. Specific labeling of kidney, stomach and adrenal was observed. In the kidney, medullary thick ascending limb and cortical and medulla ry collecting ducts were intensely labeled, while no labeling of glome ruli, 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 hybridizat ion, without evidence of labeling of the smooth muscle. These results suggest an important role for the EP3 receptor in mediating PGE2 effec ts in these tissues.