Effect of gender and sex steroids on the contractile response of canine coronary and renal blood vessels.

The effect of gender, gonadal steroids, and antiandrogen/antiestrogen-treatment on the isotonic response of isolated preparations of the left anterior descending coronary artery (LAD), left circumflex coronary artery, and renal artery and vein of sexually mature dogs was investigated. The maximum isotonic response of the coronary and renal vasculature to the thromboxane A2 (TXA2)-mimetic U46619 was significantly greater, and the EC50 value was significantly lower in males as compared with females. Moreover, similar gender differences in the contractile response of the coronary vasculature to norepinephrine were observed. Pretreatment of male dogs with the antiandrogens flutamide or cyproterone acetate reduced the maximum contractile response of the LAD to the TXA2-mimetic. Pretreatment of female dogs with testosterone resulted in an increase in both the maximum contractile response and EC50 value to U46619. Antiestrogen treatment of female dogs with tamoxifen was associated with an increase in the maximum contractile response of the LAD to U46619. Estrogen pretreatment of male dogs decreased both the maximum contractile response and the EC50 value to U46619. Therefore, there is a sex difference in LAD and LCX contractile responses to both U46619 and norepinephrine. These results suggest that smooth muscle reactivity of dog coronary artery to the TXA2-mimetic U46619 may be susceptible to regulation by both androgens and estrogens. The observed gender differences in the catecholamine response may be similarly altered by changes in the hormonal milieu.