title: Sarcoplasmic-endoplasmic reticulum Ca2+-ATPase inhibition prevents endothelin A receptor antagonism in rat aorta.
abstract: This study tested whether sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase regulates the ability of endothelin receptor antagonist to inhibit the endothelin-1 constriction. The endothelin A receptor antagonist BQ-123 (1 microM) completely relaxed constriction to 10 nM endothelin-1 in endothelium-denuded rat aorta. Challenge with cyclopiazonic acid (10 microM), a sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase inhibitor, during the plateau of endothelin-1 constriction enhanced the constriction by approximately 30%. BQ-123 relaxed the endothelin-1 plus cyclopiazonic acid constriction by only approximately 10%. In contrast, prazosin (1 microM), an alpha-adrenergic receptor antagonist, still completely relaxed the 0.3 muM phenylephrine constriction in the presence of cyclopiazonic acid. Verapamil relaxed the endothelin-1 plus cyclopiazonic acid constriction by approximately 30%, whereas Ni(2+) and 2-aminoethoxydiphenyl borate, nonselective cation channel and store-operated channel blockers, respectively, completely relaxed the constriction. These results suggest that lowered sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase activity selectively decreases the ability of endothelin receptor antagonist to inhibit the endothelin A receptor. The decreased antagonism may be related to the opening of store-operated channels and subsequent greater internalization of endothelin A receptor.
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, Ege University, Izmir, Turkey. metiner.tosun@ege.edu.tr
authors.forename: M
authors.initials: M
authors.lastname: Tosun
authors.forename: Y
authors.initials: Y
authors.lastname: Erac
authors.forename: C
authors.initials: C
authors.lastname: Selli
authors.forename: N
authors.initials: N
authors.lastname: Karakaya
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001013:Aorta, Thoracic; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004347:Drug Interactions; D004721:Endoplasmic Reticulum / Q000201:enzymology; D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000201:enzymology*; D010456:Peptides, Cyclic / Q000494:pharmacology*; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000959:Antihypertensive Agents; D065130:Endothelin A Receptor Antagonists; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D007211:Indoles; D010456:Peptides, Cyclic; D044022:Receptor, Endothelin A; D010656:Phenylephrine; D000252:Calcium-Transporting ATPases; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D002118:Calcium; C000543:cyclopiazonic acid; D011224:Prazosin