title: Angiotensin II contractions in coronary artery. Nature of receptors and calcium pools.
abstract: Pig coronary artery rings denuded of endothelium contract to the vasoactive hormone angiotensin II (Ang II). The nature of Ang II receptors and their Ca(2+)-pool utilization were examined for contraction of the artery rings and for increase in ultracellular [Ca2+] ([Ca2+]i) in smooth muscle cells cultured from them. Ang II contracted the arteries (EC50 = 7 +/- 4 nM) but with a lower maximal force (1.4 +/- 0.25 N/g tissue) than the contraction with 60 mM K+ (6.11 +/- 0.63 N/g tissue). In the cultured cells it caused a transient increase in [Ca2+]i with an EC50 value of 11 +/- 4 nM. The cells bound Ang II with a dissociation constant (Kd) of 7 +/- 2 nM. Based on the effects of the Ang II antagonists saralasin, DuPont 753, dithiothreitol and PD123319, the Ang II receptors responsible for contraction, increase in [Ca2+]i and Ang II binding to coronary artery smooth muscle were of type AT1. The contraction to Ang II was abolished by EGTA but not by nitrendipine. The sarcoplasmic Ca2+ pump inhibitors cyclopiazonic acid (10 microM CPA) and thapsigargin (1 microM) produced contractions of 4.35 +/- 0.73 and 2.07 +/- 0.54 N/g, respectively. Ang II contractions in the control arteries were nearly abolished upon pretreatment with CPA and thapsigargin. CPA and thapsigargin induced contractions were abolished by exposure to EGTA for 1 h but short exposure of the cells to EGTA only modulated the CPA or thapsigargin induced increase in [Ca2+]i; Ang II induced increase in [Ca2+]i was not inhibited by 1 microM nitrendipine but was reduced significantly by a 30-60 sec exposure to EGTA.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
authors: A K
authors: AK
authors: Grover
authors: V P
authors: VP
authors: Fomin
authors: S E
authors: SE
authors: Samson
mesh_terms: D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000187:drug effects*; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D008954:Models, Biological; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D009568:Nitrendipine / Q000494:pharmacology; D011945:Receptors, Angiotensin / Q000378:metabolism; D013552:Swine
chemical_list: D011945:Receptors, Angiotensin; D000804:Angiotensin II; D004533:Egtazic Acid; D009568:Nitrendipine