Abstract

AIM:

To determine the role of endothelium-derived contracting factor (EDCF) in the response to endothelin-1 in arteries with regenerated endothelium.

METHODS:

Rings of porcine coronary arteries, with and without endothelium of previously deendothelialized left anterior descending coronary arteries and native left circumflex coronary arteries, were suspended in conventional organ chambers for the measurement of isometric force.

RESULTS:

In quiescent rings of the previously deendothelialized left anterior descending coronary artery treated with the NO-synthase inhibitor nitro-L-arginine, endothelin-1 caused contractions which were larger in rings with than that in those without endothelium. Under the same experimental conditions, in the left circumflex coronary artery, the contractions to endothelin-1 were augmented markedly by the removal of the endothelium. In rings with endothelium of the previously deendothelialized left anterior descending coronary artery, indometacin (inhibitor of cyclooxygenase) and ridogrel (thromboxane A2 receptor antagonist and inhibitor of thromboxane synthase) inhibited contractions to endothelin-1. Dazoxiben (inhibitor of thromboxane synthase) inhibited, to the same extent as indometacin and ridogel, the response to higher concentrations of endothelin-1. The endothelium-dependent component of the response to lower concentrations of endothelin-1 was inhibited by indometacin and ridogrel, but not by dazoxiben. In rings without endothelium of both previously deendothelialized left anterior descending and native left circumflex coronary arteries, indometacin and ridogrel did not affect the contractions to endothelin-1.

CONCLUSION:

These findings suggest that in regenerated endothelium, high concentrations of endothelin-1 stimulate the release of thromboxane A2. Endoperoxides generated by activation of endothelial cyclooxygenase may be the endothelium-derived contracting factor(s) released in regenerated endothelium by lower concentrations of the peptide.