Flow-dependent, endothelium-mediated dilation of epicardial coronary arteries in conscious dogs: effects of cyclooxygenase inhibition

J Cardiovasc Pharmacol. Nov-Dec 1984;6(6):1161-9.


Endothelial damage or removal abolishes the dilation of epicardial coronary arteries induced by increments in flow through these arteries in vitro. Therefore, we tested whether or not the release of a cyclooxygenase product from endothelial cells in vivo is the mechanism of this flow-dependent dilation. In eight conscious dogs, instrumented to register the external diameter of two epicardial branches--anterior descending and circumflex--of the left coronary artery, increments in coronary flow increased and reductions in coronary flow decreased the diameter of the left circumflex epicardial artery by 182 +/- 11 micron/100% change in flow. When mean coronary flow in one epicardial branch was kept constant by a distal, flow-limiting stenosis during the application of flow-augmenting stimuli (temporal coronary occlusion or 80-400 micrograms/kg adenosine i.v.), no dilation of this artery was observed. Cyclooxygenase inhibition (suppressing the bradykinin-induced elevation of plasma 6-keto-PGF1 alpha) by indomethacin (5 mg/kg) or by diclofenac (10 mg/kg) increased smooth muscle tone in both epicardial arteries, but did not modify the flow-diameter relation (181 +/- 10 and 179 +/- 9 microns/100% change in flow, respectively). It is concluded that a tonic, instantaneous influence of coronary flow on the smooth muscle tone of the epicardial coronary arteries exists in vivo. It is unlikely that prostacyclin or another prostanoid is a mediator of this endothelium-mediated influence of flow on smooth muscle tone.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 6-Ketoprostaglandin F1 alpha / blood
  • Adenosine / pharmacology
  • Animals
  • Blood Pressure / drug effects
  • Coronary Circulation / drug effects*
  • Coronary Vessels / drug effects*
  • Cyclooxygenase Inhibitors*
  • Dogs
  • Endothelium / drug effects
  • Ergonovine / pharmacology
  • Female
  • Heart Rate / drug effects
  • Hyperemia / physiopathology
  • Male
  • Nitroglycerin / pharmacology
  • Vasodilation / drug effects*


  • Cyclooxygenase Inhibitors
  • 6-Ketoprostaglandin F1 alpha
  • Nitroglycerin
  • Adenosine
  • Ergonovine