Androgen deprivation, estrogen treatment and vascular function in male rataorta

The beneficial effects of estrogen on arterial function in women are well e stablished, 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 in tact and castrated rats, which had been implanted with capsules containing either 17 beta-estradiol (E-2) or its vehicle for 5 days. Contractile respo nses to noradrenaline were potentiated by castration and by E-2 treatment. Concentration-response curves for N-methyl-L-arginine and superoxide dismut ase indicated that the tone-related release of NO increased in tissues from castrated, compared with intact rats, but was not affected by E-2 treatmen t. Endothelium-dependent relaxation elicited by carbachol and histamine wer e not altered by castration and were attenuated by E-2 in preparations from intact, but not from castrated rats. Moreover, aortic prostacyclin release dropped by about 40% after E-2 treatment in tissues from both intact and c astrated animals. Similarly, smooth muscle sensitivity to NO significantly decreased following castration and E-2 treatment, as assessed by responses to sodium nitroprusside. Finally, no differences among groups were detected in platelet thromboxane A(2) production. Thus, vascular responses in male rats were not improved by androgen deprivation alone or by E-2 treatment, w hose effects differed in the presence or absence of androgens. These findin gs provide evidence for the gender specificity of the vascular effects of e strogen and may be consistent with a beneficial role of physiologic levels of male sex hormones in arterial function.