Effects of vasopressin on arterial blood pressure and cardiac output in male and female rats

Abstract

This study was performed to investigate further the mechanisms underlying the sexual dimorphism of the pressor responses to vasopressin. We have confirmed our earlier findings that the pressor response to graded infusions of vasopressin in conscious unrestrained male rats is similar to that in estrous females and greater than in diestrus, proestrus, and metestrus. This difference was due primarily to greater increases in total peripheral resistance (TPR) in males and estrous females, since there were no sex- or cycle-related differences in the vasopressin-induced reductions in cardiac output. Gonadectomy was without effect in males but, in females, increased blood pressure responses to vasopressin to levels found in males. Chronic treatment of ovariectomized rats with estradiol reduced pressor responsiveness to vasopressin; treatment with progesterone was without effect. These differences were also due to differences in TPR. It is concluded that the sex- and cycle-dependent differences in vasopressin-induced increases in blood pressure are due largely to attenuation of increases in TPR by estrogen.