Effects of Estradiol-17β and Progesterone on Endothelial Cell Morphology of Ovine Uterine Arteries1

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Abstract
The effect of ovarian steroids on the morphology of endothelial cells of ovine uterine arteries was studied utilizing scanning and transmission electron microscopy. Uterine arteries ipsilateral or contralateral to the ovary bearing a corpus luteum or corpus albicans were removed from ewes at various stages of the estrous cycle. Fewer endothelial cells (P < 0.01) extended into the lumen of the ipsilateral than of the contralateral artery regardless of the stage of the cycle studied. The majority of endothelial cells in the ipsilateral arteries were flat and spindle-shaped. To determine if the differences observed were due to the local effects of estrogen or progesterone (P4), ovariectomized ewes were treated for 1 wk with estradiol (E2), P4 or E2 + P4. Arteries removed from ewes receiving twice daily injections of P4 or a combination of implanted E2 + P4 had fewer endothelial cells extending into the lumen (P < 0.01) compared with arteries of control or E2-treated ewes. The number of extended endothelial cells per 25 .mu.m2 of uterine arteries of control and E2-implanted ewes did not differ significantly. Ovarian apparently P4 secretion has a marked influence on endothelial cell morphology of the ipsilateral uterine artery.