LAUSR

ABSTRACT At arterial sites of endothelial denudation and dysfunction, activated platelets contribute to vascular injury through the release of potent contracting factors such as serotonin (5‐HT). This study evaluated whether omega‐3 polyunsaturated fatty acids (PUFAs), known to protect the vascular system, are able to prevent platelets‐induced contractile responses in isolated arteries and, if so, to investigate the underlying mechanism and the importance of the omega‐3 PUFAs formulation. Porcine coronary arteries (PCA), human internal mammary arteries (IMA) and washed human platelets were prepared and vascular reactivity was studied in organ chambers. In PCA rings, aggregating platelets caused concentration‐dependent contractions that were significantly inhibited by the 5‐HT2A receptor antagonist ketanserin, and by EPA:DHA 6:1 but not EPA:DHA 1:1 at 0.4% v/v. EPA:DHA 6:1 also prevented the 5‐HT‐induced contractions but affected only slightly those to the thromboxane A2 analogue U46619. The inhibitory effect of EPA:DHA 6:1 on platelets‐induced contractions was not observed in rings without endothelium, and prevented by an eNOS inhibitor but not by inhibitors of endothelium‐dependent hyperpolarization. In IMA rings, EPA:DHA 6:1 but not EPA:DHA 1:1 at 0.4% v/v significantly prevented the 5‐HT‐induced contraction, and induced greater endothelium‐dependent relaxations than bradykinin and acetylcholine sensitive to an eNOS inhibitor. EPA:DHA 6:1 strongly inhibits platelets‐ and 5‐HT‐induced contractions in PCA rings and those to 5‐HT in IMA rings most likely through an increased endothelial formation of NO. These findings suggest that the omega‐3 PUFAs EPA:DHA 6:1 formulation may be of interest to prevent platelets‐induced vascular injury at arterial sites of endothelial dysfunction.