Effect of extracellular calcium concentration on angiotensin AT1 receptor-mediated smooth muscle contraction and antagonism in rabbit aorta.
Angiotensin-II (AII) stimulates smooth muscle contraction by activating angiotensin AT1 receptor which induces intracellular Ca2+ release and Ca2+ influx from extracellular space. In this study, effect of extracellular Ca2+ concentration ([Ca2+]0) on angiotensin AT1 receptor-mediated contractile response to AII has been examined in the absence and presence of [Sar1,Ala8]AII in rabbit aorta. A decrease in agonist potency and an increase in antagonist potency for depression were observed in low [Ca2+]0. Data were interpreted by applying an explanatory model developed previously. The result indicates that [Ca2+]0 is linked to the efficacy expression of AII at angiotensin AT1 receptor and this prompted speculation about the underlying mechanism.
Liu
Y J
YJ
Department of Analytical Pharmacology, King's College School of Medicine and Dentistry, Rayne Institute, London, UK.
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D011817:Rabbits; D011945:Receptors, Angiotensin / Q000187:drug effects / Q000378:metabolism*
D011945:Receptors, Angiotensin; D000804:Angiotensin II; D002118:Calcium