The effects of 17β-estradiol on different vessels with and without endothelium. The effect of 17β-estradiol on vessels is expressed as the percentage relaxation of the maximum contraction induced by PGF2α. The relaxant effect of 17β-estradiol at each dose was similar in all groups (n = 22 for each group, p > 0.05 by repeated-measures analysis of variance). No intra-group significant difference was found between the same vessels with and without endothelium (data not shown). 17β-estradiol has a similar vasoactive effect on both epicardial coronaries and septal branch and arteries usually used as graft in myocardial revascularization at each concentration.