androgen deprivation estrogen treatment and vascular function in male rat aorta the beneficial effects of estrogen on arterial function in women are well established whereas studies concerning the vascular role of androgens have produced conflicting results in the present study we examined the effects of androgen deprivation and of estrogen treatment on vascular responses in male rats vascular reactivity was studied in aortic rings excised from intact and castrated rats which had been implanted with capsules containing either 17betaestradiol e2 or its vehicle for 5 days contractile responses to noradrenaline were potentiated by castration and by e2 treatment concentrationresponse curves for nmethyllarginine and superoxide dismutase indicated that the tonerelated release of no increased in tissues from castrated compared with intact rats but was not affected by e2 treatment endotheliumdependent relaxation elicited by carbachol and histamine were not altered by castration and were attenuated by e2 in preparations from intact but not from castrated rats moreover aortic prostacyclin release dropped by about 40 after e2 treatment in tissues from both intact and castrated animals similarly smooth muscle sensitivity to no significantly decreased following castration and e2 treatment as assessed by responses to sodium nitroprusside finally no differences among groups were detected in platelet thromboxane a2 production thus vascular responses in male rats were not improved by androgen deprivation alone or by e2 treatment whose effects differed in the presence or absence of androgens these findings provide evidence for the gender specificity of the vascular effects of estrogen and may be consistent with a beneficial role of physiologic levels of male sex hormones in arterial function