Long-Term Hypoxia Changes Myometrial Responsiveness and Oxytocin Receptors in the Pregnant Ewe: Differential Effects on Longitudinal Versus Circular Smooth Muscle
Previous studies from our laboratory demonstrated that long-term hypoxia (LTH) altered in vitro contractile responses to oxytocin in full-thickness myometrial strips from pregnant sheep. The present study was designed to determine, first, if the reduced contractile response to oxytocin following LTH...
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Published in | Biology of reproduction Vol. 69; no. 5; pp. 1500 - 1505 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Madison, WI
Society for the Study of Reproduction
01.11.2003
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Subjects | |
Online Access | Get full text |
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Summary: | Previous studies from our laboratory demonstrated that long-term hypoxia (LTH) altered in vitro contractile responses to oxytocin
in full-thickness myometrial strips from pregnant sheep. The present study was designed to determine, first, if the reduced
contractile response to oxytocin following LTH is the result of combined effects on longitudinal and circular smooth muscle
or if the effect is specific to a single muscle layer and, second, if the reduced contractile response to oxytocin following
LTH is caused by changes in oxytocin-receptor protein. Pregnant ewes were maintained at high altitude (3820 m) from Day 30
to Days 137â142 of gestation, when the ewes were killed for collection of myometrial tissue. Tissue was also collected from
age-matched, normoxic controls. Longitudinal and circular layers were separated, length-tension curves generated to determine
optimal resting tension, and all strips exposed to increasing half-log doses of oxytocin ranging from 10 â12 to 10 â6.5 M. The expression of oxytocin-receptor protein was measured using Western blot analysis. We found that LTH did not affect
KCl-induced contraction of either smooth muscle layer, whereas the sensitivity of both myometrial layers to oxytocin was altered.
A decreased maximum contractile response of the circular layer to oxytocin was also observed. Additionally, LTH decreased
expression of oxytocin-receptor protein in the circular layer and increased levels in the longitudinal layer. Results from
the present study indicate that LTH alters contractile responses and oxytocin-receptor protein expression in a layer-specific
manner in the pregnant sheep myometrium. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0006-3363 1529-7268 |
DOI: | 10.1095/biolreprod.103.018556 |