Effects of Inhibitors of Arachidonic Acid Metabolism and Calcium Entry on Responses to Acetylcholine, Potassium and

The present study was designed to determine whether interfer-ence with the metabolism of arachidonic acid or the entry of extracellular calcium affects the responses of the canine saphen-ous vein to acetylcholine, potassium or norepinephrine. Rings of canine saphenous vein, with or without endothelium, were sus-pended inorgan chambers filled with physiological salt solution and set at their optimal length for isometric tension recording. Removal of the endothelium, confirmed by the absence of the characteristic relaxation induced by thrombin in intact rings, did not affect concentration-response curves to acetylcholine or norepinephnne. The cyclooxygenase inhibitor, indomethacin, augmented the response to acetylcholine. This effect was com-parable in rings with and without endothelium and in rings pretreated with phentolamine. lndomethacin did not alter the response to norepinephnne but augmented that to potassium