Nonpeptidic urotensin-II receptor antagonists I: in vitro pharmacological characterization of SB-706375.
1. SB-706375 potently inhibited [(125)I]hU-II binding to both mammalian recombinant and 'native' UT receptors (K(i) 4.7+/-1.5 to 20.7+/-3.6 nM at rodent, feline and primate recombinant UT receptors and K(i) 5.4+/-0.4 nM at the endogenous UT receptor in SJRH30 cells). 2. Prior exposure to SB-706375 (1 microM, 30 min) did not alter [(125)I]hU-II binding affinity or density in recombinant cells (K(D) 3.1+/-0.4 vs 5.8+/-0.9 nM and B(max) 3.1+/-1.0 vs 2.8+/-0.8 pmol mg(-1)) consistent with a reversible mode of action. 3. The novel, nonpeptidic radioligand [(3)H]SB-657510, a close analogue of SB-706375, bound to the monkey UT receptor (K(D) 2.6+/-0.4 nM, B(max) 0.86+/-0.12 pmol mg(-1)) in a manner that was inhibited by both U-II isopeptides and SB-706375 (K(i) 4.6+/-1.4 to 17.6+/-5.4 nM) consistent with the sulphonamides and native U-II ligands sharing a common UT receptor binding domain. 4. SB-706375 was a potent, competitive hU-II antagonist across species with pK(b) 7.29-8.00 in HEK293-UT receptor cells (inhibition of [Ca(2+)](i)-mobilization) and pK(b) 7.47 in rat isolated aorta (inhibition of contraction). SB-706375 also reversed tone established in the rat aorta by prior exposure to hU-II (K(app) approximately 20 nM). 5. SB-706375 was a selective U-II antagonist with >/=100-fold selectivity for the human UT receptor compared to 86 distinct receptors, ion channels, enzymes, transporters and nuclear hormones (K(i)/IC(50)>1 microM). Accordingly, the contractile responses induced in isolated aortae by KCl, phenylephrine, angiotensin II and endothelin-1 were unaltered by SB-706375 (1 microM). 6. In summary, SB-706375 is a high-affinity, surmountable, reversible and selective nonpeptide UT receptor antagonist with cross-species activity that will assist in delineating the pathophysiological actions of U-II in mammals.
Douglas
Stephen A
SA
CVU Department of Biology, Cardiovascular and Urogenital and Respiratory and Inflammation Centers of Excellence for Drug Discovery, GlaxoSmithKline, 709 Swedeland Road, UW2510 King of Prussia, PA 19406-0939, USA. steve.a.douglas@gsk.com
Behm
David J
DJ
Aiyar
Nambi V
NV
Naselsky
Diane
D
Disa
Jyoti
J
Brooks
David P
DP
Ohlstein
Eliot H
EH
Gleason
John G
JG
Sarau
Henry M
HM
Foley
James J
JJ
Buckley
Peter T
PT
Schmidt
Dulcie B
DB
Wixted
William E
WE
Widdowson
Katherine
K
Riley
Graham
G
Jin
Jian
J
Gallagher
Timothy F
TF
Schmidt
Stanley J
SJ
Ridgers
Lance
L
Christmann
Lisa T
LT
Keenan
Richard M
RM
Knight
Steven D
SD
Dhanak
Dashyant
D
D000465:Algorithms; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D001667:Binding, Competitive / Q000187:drug effects; D002415:Cats; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D000882:Haplorhini; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D011759:Pyrrolidines / Q000494:pharmacology*; D011869:Radioligand Assay; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors* / Q000235:genetics*; D011994:Recombinant Proteins / Q000378:metabolism; D012208:Rhabdomyosarcoma / Q000378:metabolism; D013045:Species Specificity; D013449:Sulfonamides / Q000494:pharmacology*; D000096926:Benzenesulfonamides
D011759:Pyrrolidines; D043562:Receptors, G-Protein-Coupled; D011994:Recombinant Proteins; D013449:Sulfonamides; C504940:SB-706375; D000096926:Benzenesulfonamides; C121697:UTS2R protein, human