Fig. 1. Effects of etomidate (A and B ) and ketamine (C and D ) on the endothelium-dependent relaxation induced by acetylcholine in pulmonary arteries. Arterial rings were precontracted to the ED50level of tension with phenylephrine. Relaxation responses are expressed as the percentage of phenylephrine precontraction. Etomidate (10−5m) had little effect (A ), whereas etomidate (10−4m) significantly attenuated (* P < 0.05) the relaxation induced by acetylcholine (B ). Ketamine also inhibited (* P < 0.05) acetylcholine-induced relaxation at a concentration of 10−4m (D ) but not at 10−5m (C ).