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Role of endothelin in alpha-adrenoceptor coronary vasoconstriction

Mark W Gorman1, Martin Farias, Keith N Richmond

  • 1Dept. of Physiology and Biophysics, Box 357290, University of Washington School of Medicine, Seattle, WA 98195-7290, USA. mgorman@u.washington.edu

American Journal of Physiology. Heart and Circulatory Physiology
|December 14, 2004
PubMed

Insights

Alpha-adrenoceptor coronary vasoconstriction during exercise is not mediated by endothelin. While endothelin causes vasoconstriction at rest, alpha-adrenoceptor activation during exercise does not rely on endothelin signaling.

Area of Science:

  • Cardiovascular Physiology
  • Pharmacology

Background:

  • Alpha-adrenoceptors on cardiac myocytes may stimulate endothelin release, causing coronary vasoconstriction.
  • The role of endothelin in exercise-induced alpha-adrenoceptor mediated coronary vasoconstriction is unclear.

Purpose of the Study:

  • To test if alpha-adrenoceptor-mediated coronary vasoconstriction during exercise is due to endothelin.

Main Methods:

  • Conscious dogs were treated with endothelin receptor antagonist tezosentan or alpha-adrenoceptor antagonist phentolamine during rest and exercise.
  • Anesthetized dogs received intracoronary alpha-adrenoceptor agonist phenylephrine with or without tezosentan.

Main Results:

  • Tezosentan increased coronary venous oxygen tension at rest but not during exercise.
  • Phentolamine increased coronary venous oxygen tension during exercise but not at rest.
  • Phenylephrine caused coronary vasoconstriction partially blocked by tezosentan, suggesting high catecholamine levels are needed for alpha-adrenoceptor-induced endothelin release.

Conclusions:

  • Alpha-adrenoceptor-mediated coronary vasoconstriction during exercise is not dependent on endothelin.
  • Endothelin contributes to basal coronary vasoconstriction at rest.
  • Alpha-adrenoceptor-induced endothelin release likely requires pharmacological concentrations of catecholamines not achieved during physiological exercise.

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