Differential effects of prostanoid synthesis inhibitors on cicletanine-induced relaxation of isolated human epigastric arteries.

We have examined the influence of prostanoid synthesis inhibitors on the relaxation responses induced by cicletanine in ring preparations of isolated human epigastric arteries following precontraction induced by 10(-7) M noradrenaline. Cicletanine caused concentration-dependent relaxations, uninfluenced by the cyclooxygenase inhibitors, meclofenamate (1, 10 microM) and indomethacin (1, 10 microM) but significantly (p < 0.05) attenuated by the specific prostacyclin synthesis inhibitor, tranylcypromine (0.1-10 microM) (n > 6 in each). In contrast, cromakalim-induced relaxations were significantly attenuated by indomethacin, meclofenamate and tranylcypromine. The tranylcypromine-sensitive cicletanine-induced relaxation suggests, at least in part, the involvement of prostacyclin in the vasodilator action of cicletanine.