title: On the quantitation of an agonist with dual but opposing components of action: application to vascular endothelial relaxation.
abstract: In this communication we show that the same principle that underlies the use of the isobolograph for assessing agonist interactions also leads to a method for analyzing the opposing effects of a single agonist. This is the principle of dose equivalence whose application is illustrated here and applied to the endothelium-dependent relaxing component of two putative vasoconstrictor peptides. These studies, employing angiotensin II and endothelin-1, were conducted with isolated preparations of rat aorta that were measured for agonist-induced isometric tension development in both endothelial-denuded and -intact vessels. The dose-effect relation of the relaxing component of each agonist, which should not be calculated from simple effect subtraction, was derived by the method described here.
authors.affiliation: Department of Pharmacology and Center for Substance Abuse Research, Temple University School of Medicine, Philadelphia, PA 19140, USA.
authors.forename: Neil S
authors.initials: NS
authors.lastname: Lamarre
authors.forename: Tom
authors.initials: T
authors.lastname: Parry
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Tallarida
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D054313:Drug Agonism; D004347:Drug Interactions; D019332:Endothelin-1 / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D019332:Endothelin-1; D014665:Vasodilator Agents; D000804:Angiotensin II