Chronic exposure of cultured endothelial cells to eicosapentaenoic acid potentiates the release of endothelium-derived relaxing factor(s).

1. The effect of chronic exposure of cultured porcine aortic endothelial cells to eicosapentaenoic acid on the release of indomethacin-insensitive relaxing factor(s) was investigated (a) under bioassay conditions using preconstricted canine coronary artery rings without endothelium and (b) by the measurement of guanosine 3':5'-cyclic monophosphate (cyclic GMP) content of endothelial cells. 2. Exposure of endothelial cells for 8-10 days to eicosapentaenoic acid (2.5 x 10(-5) M) did not affect the relaxing activity of the perfusate from unstimulated endothelial cells. 3. The treatment with eicosapentaenoic acid significantly increased the relaxation of the bioassay ring observed upon stimulation of the endothelial cells with adenosine diphosphate (3 x 10(-8) M to 3 x 10(-4) M) and, to a lesser extent with bradykinin (10(-8) to 3 x 10(-8) M), while the relaxing activity evoked by the calcium ionophore A23187 (3 x 10(-7) M) was not affected. Neither acetylcholine (10(-6) M) nor 5-hydroxytryptamine (10(-6) M) stimulated the release of relaxing factor(s) from control or eicosapentaenoic acid-treated endothelial cells. 4. Bradykinin (10(-7) M), adenosine diphosphate (3 x 10(-5) M), the calcium ionophore A23187 (10(-6) M) and nitric oxide (2 x 10(-6) M) stimulated haemoglobin-sensitive increases in cyclic GMP content of porcine endothelial cells which were unaffected by prior chronic exposure to eicosapentaenoic acid. 5. These results suggest that chronic exposure of porcine aortic endothelial cells to eicosapentaenoic acid increases the release of relaxing factor(s) in response to activation of membrane-associated receptors for purines and kinins. The lack of effect of eicosapentaenoic acid treatment on agonist-stimulated production of cyclic GMP suggests that the enhanced relaxation observed under bioassay conditions is not due to an increased production of nitric oxide.