The effects of sex steroids on human umbilical artery and vein

OBJECTIVE: To define the vascular actions of selected sex steroids on human umbilical artery and vein and to determine whether there are any gender-specific differences in vasorelaxation between umbilical cord vessels of male and female fetuses. METHODS: Segments of umbilical artery (n = 12) and umbilical vein (n = 8) from male and female fetuses were suspended in organ baths of Krebs solution for isometric tension recording. The vessels were contracted using 60 mM potassium chloride followed by exposure to increasing concentrations (10^-7 to 10^-4 M) of sex steroid hormones (estradiol-17β, estriol, estrone, testosterone, and progesterone). A specific estrogen receptor antagonist (ICI 164,384) was used to attempt to block the estradiol effect. Changes in tension were recorded. RESULTS: Of the agents tested, estradiol-17β had the greatest effect (25-29% relaxation at 10^-4 M concentration), which was uninhibited by a specific receptor antagonist. The other steroids tested had no significant effect, even at 10^{- 4} M concentration. The umbilical artery is slightly more sensitive to the effects of estradiol than the umbilical vein. There were no gender-specific differences noted in either artery or vein harvested from male or female fetuses. CONCLUSION: Estradiol-17β in supraphysiologic concentrations has a non-receptor-mediated vasorelaxation effect on human umbilical blood vessels.