Nonpeptide endothelin receptor antagonists. XI. Pharmacological characterization of SB 234551, a high-affinity and selective nonpeptide ETA receptor antagonist.
The present study describes the pharmacological profile of ((E)-alpha-[[1-butyl-5-[2-[(2-carboxyphenyl)methoxy]-4-methoxy-phenyl ]-1H-pyrazol-4-yl]methlene]-6-methoxy-1,3-benzodioxole-5-propanoic acid) (SB 234551), a high-affinity, nonpeptide endothelin type A (ETA)-selective receptor antagonist. In human cloned ETA and endothelin type B (ETB) receptors, SB 234551 produced a concentration-dependent displacement of [125I]-endothelin-1 with Ki values of 0.13 and 500 nM, respectively. SB 234551 elicited concentration-dependent, rightward competitive shifts in the endothelin-1 concentration-response curves in isolated rat aorta and isolated human pulmonary artery (ETA receptor-mediated vascular contraction) with Kb values of 1.9 and 1.0 nM, respectively. SB 234551 antagonized ETB receptor-mediated vasoconstriction in the isolated rabbit pulmonary artery, as demonstrated by concentration-dependent, rightward shifts in the sarafotoxin S6c concentration-response curves (Kb = 555 nM). SB 234551 produced weak functional inhibition of sarafotoxin S6c-mediated endothelium-dependent relaxation (IC50 = 7 microM). SB 234551 (10 microM) had no significant effect against contraction produced by several other vasoactive agents and did not significantly influence radioligand binding to a number of diverse receptors. SB 234551 (0. 1-1.0 mg/kg i.v.) dose-dependently inhibited the pressor response to exogenous endothelin-1 in conscious rats. In vivo pharmacokinetic analysis in the rat demonstrated that SB 234551 was rapidly absorbed from the GI tract with a bioavailability of 30%. SB 234551 had a plasma half-life of 125 min and a systemic clearance of 25.0 ml/min/kg. The present study demonstrates that SB 234551 is an antagonist with high affinity for the ETA receptor, while sparing the ETB receptor. SB 234551 is a new pharmacological tool that should assist in the elucidation of the role of endothelin in pathophysiology.
Department of Cardiovascular, Renal and Pulmonary Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA.
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Ohlstein
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Nambi
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Hay
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Gellai
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Brooks
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Luengo
J N
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Xiang
J D
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Elliott
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D016466:CHO Cells; D003001:Cloning, Molecular; D006224:Cricetinae; D004149:Dioxoles / Q000494:pharmacology*; D065128:Endothelin Receptor Antagonists; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D011720:Pyrazoles / Q000494:pharmacology*; D011817:Rabbits; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A
D004149:Dioxoles; D065128:Endothelin Receptor Antagonists; D011720:Pyrazoles; D044022:Receptor, Endothelin A; C113973:SB 234551