Gender Differences in Hemodynamic Responses to Endothelin-1

We investigated whether gender affects the pressor and constrictor effects of endothelin-1 (ET-1) in anesthetized rats. Baseline values for arterial blood pressure (mmHg) and hindquarter resistance (HQR, mmHg/ml/min/100 g), respectively, were similar in male (96.0 +/- 3.1 and 13.9 +/- 0.6) and female (103.1 +/- 5.6 and 12.8 +/- 2.3) rats. ET-1 (1 and 3 microg/kg) produced rapid and transient falls in arterial blood pressure and HQR, followed by long-lasting increases in blood pressure and HQR. The initial ET-1-induced hypotension and vasodilation were similar in both groups. However, the pressor and hindquarter vasoconstrictor effects were significantly higher (p < 0.05) in male than female rats. Thus, the increases in blood pressure and HQR to ET-1 (3 microg/kg) were attenuated in female (+15.3 +/- 3.4 mmHg and +3.7 +/- 1.6 mmHg/ml/min/100 g) compared to male (+24.9 +/- 2.3 mmHg and +8.0 +/- 1.6 mmHg/ml/ min/100 g) rats. These results indicate that there is a gender difference in the vasoconstrictor, but not the vasodilator effects of ET-1. We suggest that the lower ET-1-induced hypertension and hindlimb vasoconstrictions observed in female rats may be responsible for the lower risk of developing coronary heart disease in premenopausal women.