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Am J Obstet Gynecol. 1997 Jul;177(1):215-21.

Myoendometrial versus placental uterine arteries: structural, mechanical, and functional differences in late-pregnant rabbits.

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1
Department of Surgery, Oregon Health Sciences University, Portland 97201, USA.

Abstract

OBJECTIVE:

This study compared late-pregnant radial uterine arteries that supplied the placenta versus the myoendometrium to evaluate differences in active and passive mechanical properties.

STUDY DESIGN:

Pressurized segments of placental versus myoendometrial radial uterine arteries from late-pregnant (day 28 to 30) New Zealand White rabbits (n = 12) were compared in vitro for differences in luminal diameter, wall thickness, distensibility, and intrinsic tone as a function of transmural pressure.

RESULTS:

Both types of arteries responded to increased transmural pressure with active vasoconstriction; however, the amount of tone present in myoendometrial arteries was significantly greater than in placental arteries (percent tone at 75 mm Hg = 39% +/- 3% for myoendometrial versus 31% +/- 2% for placental arteries, p < 0.01). Measurements of unpressurized, fully relaxed arteries revealed that placental arteries were 38% larger in diameter and had thicker walls than myoendometrial arteries did. However, myoendometrial arteries were significantly more distensible at transmural pressures >5 mm Hg.

CONCLUSIONS:

The increased size and diminished tone of placental compared with adjacent myoendometrial arteries would favor increased blood flow to the placenta; differences in size and passive mechanical properties suggest that a localized factor(s) originating from the fetus or placenta contributes to the gestational enlargement of those arteries that perfuse the placenta.

PMID:
9240609
[Indexed for MEDLINE]
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