Role of endothelin in α-adrenoceptor coronary vasoconstriction

Mark W. Gorman, Martin Farias, Keith N. Richmond, Johnathan D. Tune, Eric O. Feigl

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

It has been proposed that α-adrenoceptor vasoconstriction in coronary resistance vessels results not from α-adrenoceptors on coronary smooth muscle but from α-adrenoceptors on cardiac myocytes that stimulate endothelin (ET) release. The present experiments tested the hypothesis that the α-adrenoceptor-mediated coronary vasoconstriction that normally occurs during exercise is due to endothelin. In conscious dogs (n = 10), the endothelin ETA/ETB receptor antagonist tezosentan (1 mg/kg iv) increased coronary venous oxygen tension at rest but not during treadmill exercise. This result indicates that basal endothelin levels produce a coronary vasoconstriction at rest that is not observed during the coronary vasodilation during exercise. In contrast, the α-adrenoceptor antagonist phentolamine increased coronary venous oxygen tension during exercise but not at rest. The difference between the endothelin blockade and α-adrenoceptor blockade results indicates that α-adrenoceptor coronary vasoconstriction during exercise is not due to endothelin. However, in anesthetized dogs, bolus intracoronary injections of the α-adrenoceptor agonist phenylephrine produced reductions in coronary blood flow that were partially antagonized by endothelin receptor blockade with tezosentan. These results are best explained if α-adrenoceptor-induced endothelin release requires high pharmacological concentrations of catecholamines that are not reached during exercise.

Original languageEnglish
Pages (from-to)H1937-H1942
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume288
Issue number4 57-4
DOIs
StatePublished - Apr 2005

Keywords

  • Coronary blood flow
  • Dogs
  • Exercise
  • Norepinephrine
  • Tezosentan

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