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-sp ecific 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 60mM potass ium chloride followed by exposure to increasing concentrations (10(-7) to 1 0(-4) M) of sex steroid hormones (estradiol-17 beta, estriol, estrone, test osterone, and progesterone). A specific estrogen receptor antagonist (ICI 1 64,384) was used to attempt to block the estradiol effect. Changes in tensi on were recorded. RESULTS: Of the agents tested, estradiol-17 beta had the greatest effect (2 5-29% relaxation at 10(-4)M concentration), which was uninhibited by a spec ific receptor antagonist. The other steroids tested had no significant effe ct, even at 10(-4)M concentration. The umbilical artery is slightly more se nsitive to the effects of estradiol than the umbilical vein. There were no gender-specific differences noted in either artery or vein harvested from m ale or female fetuses. CONCLUSIONS: Estradiol-17 beta in supraphysiologic concentrations has a non -receptor-mediated vasorelaxation effect on human umbilical blood vessels.