Pharmacology of [3H]prostaglandin E1/[3H]prostaglandin E2 and [3H]prostaglandin F2alpha binding to EP3 and FP prostaglandin receptor binding sites in bovine corpus luteum: characterization and correlation with functional data.
Specific binding of [3H]prostaglandin (PG) E1, [3H]PGE2 and [3H]PGF2alpha 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]PGF2alpha 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 > 1 microM) influenced by EP1-selective (SC-19220), FP-selective (fluprostenol, PHXA85), DP-selective (BWA868C; ZK118182), IP-selective (iloprost) and TP-selective (U46619) PGs. Specific [3H]PGF2alpha binding was potently displaced by FP-selective agents such as fluprostenol, PHXA85 and cloprostenol with nanomolar affinities (n = 3-25), but weakly (Kis > 1 microM) 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]PGF2alpha binding to FP receptors in washed bovine corpus luteum homogenates.
Sharif
N A
NA
Molecular Pharmacology Unit, Alcon Laboratories Inc., Fort Worth, Texas 76134-2099, USA.
Xu
S X
SX
Williams
G W
GW
Crider
J Y
JY
Griffin
B W
BW
Davis
T L
TL
D000527:Alprostadil / Q000378:metabolism*; D000818:Animals; D001345:Autoradiography; D002417:Cattle; D003338:Corpus Luteum / Q000187:drug effects / Q000378:metabolism*; D015237:Dinoprost / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D011982:Receptors, Prostaglandin / Q000187:drug effects* / Q000378:metabolism*; D018078:Receptors, Prostaglandin E / Q000187:drug effects* / Q000378:metabolism*
D010716:Phosphatidylinositols; D011982:Receptors, Prostaglandin; D018078:Receptors, Prostaglandin E; D015237:Dinoprost; D000527:Alprostadil; D015232:Dinoprostone