Endothelin and effects of endothelin-receptor activation in the mammary and radial artery.

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Abstract
Objective—To determine the tissue content and endothelin‐receptor characteristics of endothelin‐1 in the radial artery in relation to the internal mammary artery. Design—Endothelin‐1 content was quantified in the radial artery and the internal mammary artery. Both arteries were exposed to endothelin‐1 and agonists of the endothelin A and B receptors. Results—The highest level of endothelin‐1 was found in the radial artery. Endothelin‐1 contracted both arteries. The contraction was sensitive to endothelin A ‐receptor agonism and enhanced in both arteries by inhibition of prostacyclin and nitric oxide formation. In the internal mammary artery the endothelin B ‐receptor agonist caused an endothelin A ‐receptor sensitive contraction augmented by inhibition of nitric oxide and prostacyclin. However, in the radial artery this contraction was only observed in the presence of inhibition of nitric oxide and prostaglandin. Conclusion—The highest endothelin‐1 content was found in the radial artery. The functional effects of endothelin‐1 in the radial artery were similar to that in the internal mammary artery, mediated by predominantly endothelin A ‐receptor activation causing vasoconstriction. Selective endothelin A ‐receptor blockade may prove beneficial in preventing graft spasm in the radial as well as the internal mammary artery.