Effect of ouabain on large coronary artery diameter.
Cardiac glycosides have previously been shown to constrict small coronary resistance vessels. This study evaluated the effect of a bolus intravenous dose of ouabain (20 micrograms/kg) on large left circumflex coronary arterial diameter measured by sonomicrometry in nine awake chronically instrumented dogs. Between 5 and 10 min after ouabain administration external circumflex coronary diameter decreased (3.87 +/- 0.21 to 3.83 +/- 0.21 mm, p less than 0.05). Twenty minutes after ouabain administration, coronary diameter had returned to control. At the time of the peak decrease in coronary diameter, heart rate had decreased (104 +/- 7 to 82 +/- 7 beats/min, p less than 0.05), circumflex coronary blood flow had decreased (45 +/- 7 to 38 +/- 6 ml/min, p less than 0.05), total circumflex coronary resistance had increased (2.7 +/- 0.4 to 3.5 +/- 0.6 U, p less than 0.05) and aortic pressure was unchanged (108 +/- 4 to 113 +/- 4 mm Hg). Alpha-adrenergic blockade with phentolamine did not prevent the decrease in circumflex coronary arterial diameter in each of five dogs (3.67 +/- 0.28 to 3.60 +/- 0.28 mm, p less than 0.05). Therefore, intravenous ouabain caused vasoconstriction of large coronary arteries. These vasocontrictor effects were not mediated by alpha-adrenergic mechanisms. This constriction could have important consequences in the presence of coronary stenoses.
Schwartz
J S
JS
Department of Medicine, University of Minnesota Medical School, Minneapolis.
Bache
R J
RJ
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003331:Coronary Vessels / Q000033:anatomy & histology / Q000187:drug effects*; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology*; D010646:Phentolamine / Q000494:pharmacology; D014465:Ultrasonics
D000317:Adrenergic alpha-Antagonists; D010042:Ouabain; D010646:Phentolamine