TY - JOUR T1 - Pharmacology of [<sup>3</sup>H]Prostaglandin E<sub>1</sub>/[<sup>3</sup>H]Prostaglandin E<sub>2</sub> and [<sup>3</sup>H]Prostaglandin F<sub>2</sub> <sub>α</sub> Binding to EP<sub>3</sub> and FP Prostaglandin Receptor Binding Sites in Bovine Corpus Luteum: Characterization and Correlation with Functional Data JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 1094 LP - 1102 VL - 286 IS - 2 AU - N. A. Sharif AU - S. X. Xu AU - G. W. Williams AU - J. Y. Crider AU - B. W. Griffin AU - T. L. Davis Y1 - 1998/08/01 UR - http://jpet.aspetjournals.org/content/286/2/1094.abstract N2 - Specific binding of [3H]prostaglandin (PG) E1, [3H]PGE2 and [3H]PGF2α to washed total particulate homogenates of bovine corpus luteum comprised 60 to 82% of total binding. Scatchard analysis of competition data revealed the presence of an apparent single population of binding sites for [3H]PGE1 and [3H]PGE2 with dissociation constants (Kds) of 2.76 to 3.39 nM and apparent receptor density (Bmax) of 1.5 to 1.56 pmol/g wet weight (n = 3–4). However, [3H]PGF2α appeared to interact with two classes/states of binding sites (Kd1 = 6.51 ± 0.65 nM, Bmax1 = 2.33 ± 0.26 pmol/g wet weight;Kd2 = 986 ± 269 nM; Bmax2 = 44.8 ± 11.3 pmol/g wet weight,n = 11). Specific [3H]PGE1 and [3H]PGE2 binding was most potently (nanomolar affinity) inhibited by PGs with high selectivity for the EP3 receptor subtype (e.g., GR63799, sulprostone, enprostil) but was weakly (Kis &gt; 1 μM) influenced by EP1-selective (SC-19220), FP-selective (fluprostenol, PHXA85), DP-selective (BWA868C; ZK118182), IP-selective (iloprost) and TP-selective (U46619) PGs. Specific [3H]PGF2α binding was potently displaced by FP-selective agents such as fluprostenol, PHXA85 and cloprostenol with nanomolar affinities (n = 3–25), but weakly (Kis &gt; 1 μM) by other PGs showing high selectivity for other PG receptor subtypes mentioned above. The relative specificities and potencies of EP3- and FP-selective PGs tested in the binding assays were confirmed using various functional assays. These studies have provided strong pharmacological evidence for the similarity of [3H]PGE1 and [3H]PGE2 binding to EP3 receptors and for [3H]PGF2α binding to FP receptors in washed bovine corpus luteum homogenates. The American Society for Pharmacology and Experimental Therapeutics ER -