Document Detail

Effect of an oxytocin antagonist on plasma oxytocin levels during nocturnal uterine contractions in the pregnant baboon.
MedLine Citation:
PMID:  12192888     Owner:  NLM     Status:  MEDLINE    
TT-235 is a potent oxytocin (OT) antagonist that blocks the action of OT at the receptor level. Previous studies have shown that pregnant baboons demonstrate nocturnal uterine contractions induced by OT as they near delivery. The purpose of this study was to evaluate the changes in plasma OT levels following uterine contraction blockage with TT-235. A tethered pregnant baboon model in its last trimester of pregnancy was used. Three blocks of arterial blood samples, immediately before, plus 1 h and plus 2 h following an OT antagonist injection, were collected once nocturnal uterine contractions were detected. Each block consisted of a continuous 10 min withdrawal with 10 samples per block (1 ml/min). A TT-235 dosage of 300 micrograms/kg and saline for control were utilized. Uterine activities were monitored as pressure changes in the amniotic fluid, and the frequency and mean amplitude of contractile activity per 10 min intervals were expressed as contractile force. Plasma OCT levels were determined by a radioimmunoassay following plasma extraction with petroleum ether. The contractile force was decreased by 77% (p < 0.05) within 2 h after TT-235 administration while it increased 23% following saline infusion. Plasma OT levels were unchanged following saline infusion while they increased 82% (p < 0.05) 2 h after the administration of TT-235. If a positive feedback existed between uterine contractions and OT release, one would expect plasma OT levels to be decreased with contractile activity following TT-235 infusion. Since this is not the case in the present study, the data suggest that there is either a negative feedback or an independent relationship between nocturnal uterine contractions and OT release.
T H An; C H Song; B C Choi; S C Pak; R Mehendale; G Flouret
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Publication Detail:
Type:  Evaluation Studies; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Gynecological endocrinology : the official journal of the International Society of Gynecological Endocrinology     Volume:  16     ISSN:  0951-3590     ISO Abbreviation:  Gynecol. Endocrinol.     Publication Date:  2002 Jun 
Date Detail:
Created Date:  2002-08-23     Completed Date:  2003-01-14     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8807913     Medline TA:  Gynecol Endocrinol     Country:  England    
Other Details:
Languages:  eng     Pagination:  173-8     Citation Subset:  IM    
Department of Anesthesiology, School of Medicine, Chosun University, Kwangju, Korea.
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MeSH Terms
Amniotic Fluid / drug effects,  physiology
Area Under Curve
Circadian Rhythm
Models, Animal
Oxytocin / analogs & derivatives*,  antagonists & inhibitors*,  blood,  drug effects*,  pharmacokinetics,  pharmacology*
Pregnancy Trimester, Third
Uterine Contraction / drug effects*
Uterus / drug effects
Reg. No./Substance:
0/ANTAG III; 50-56-6/Oxytocin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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