Potentiation by endothelin-1 and vasopressin of sympathetic vasoconstriction in male and female rats. 
The aim of this study was to analyse the modulatory role of endothelin-1 and vasopressin in sympathetic vasoconstriction, and whether there are gender differences in this modulatory role.  Electrical field stimulation (4 Hz, 0.2 ms pulse duration at supramaximal voltage of 70 V, for 1 s), applied to isolated segments from rat tail arteries, produced a contraction that was lower in the vascular segments from female than in those from male rats.  This arterial contraction was potentiated in a concentration-dependent way by endothelin-1 (10(-10)-3 x 10(-9) mol/l) and vasopressin (10(-12) - 10(-10) mol/l), and the increment produced by endothelin-1 was similar in the arteries of both, whereas the increment induced by vasopressin was higher in the arteries from male than in those from female rats.  These results suggest that endothelin-1 and vasopressin potentiate the vasoconstriction to sympathetic stimulation, and this potentiating effect of vasopressin may be higher, whereas that of endothelin-1 may be similar, in males than in females.