Effect of Castration and Androgen Treatment on Sex‐Linked Reactivity of Rat Aorta to a Thromboxane‐Mimic

In order to examine the possible role of androgens in the isotonic response of the isolated rat aorta, a highly active mimic of thromboxane was employed. The maximum response to this TXA2‐mimic U46619 was greater by 24 ± 3% (P<0.01) in the male, as compared with the female, In addition, the sensitivity of the male vessel was 35 ± 4% greater than that of the female vessel (P< 0.01). Orchiectomy decreased the maximum contractile response to the TXA2‐mimic; however, ovariectomy increased both the maximum response and sensitivity. Testosterone pretreatment (1 mg/kg intramuscularly, biweekly for two weeks) restored the response of the castrated male but did not further increase the response of the ovariectomized female. The maximum response and sensitivity of the aorta of the intact female pretreated with testosterone was increased (P<0.01). These results suggest that the response of rat aorta to a TXA2‐mimic may be regulated not only by androgens, but also by ovarian hormones.