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-17 beta, 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-17 beta 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-17 beta in supraphysiologic concentrations has a non-receptor-mediated vasorelaxation effect on human umbilical blood vessels.