(a) Concentration–response curves of the relaxation induced by 5-HT in the presence of CYP2B6, CYP2C9 and CYP2C19 in endothelium-denuded aortic rings precontracted with PE (100 nM). The inside histogram represents the relaxation elicited by SNP. (b) Effect of myoglobin (50 μM) on concentration–response curves of 5-HT- and SNP-induced relaxation in the presence of CYP2B6, CYP2C9 and CYP2C19 in endothelium-denuded rings precontracted with PE (5 mM). (c) Effect of methylene blue (30 μM) on concentration–response curves of 5-HT- and SNP-induced relaxation in the presence of CYP2B6, CYP2C9 and CYP2C19 in endothelium-denuded rings precontracted with PE (5 nM). (d) Effect of the catalase inhibitor 3-AT (50 mM), on concentration–response curves of curves of 5-HT- and SNP-induced relaxation in the presence of CYP2B6, CYP2C9 and CYP2C19 in endothelium-denuded rings precontracted with PE (5 nM). Each point is the mean±s.e. of n=6.