Document Detail


Altered arterial concentrations of placental hormones during maximal placental growth in a model of placental insufficiency.
MedLine Citation:
PMID:  10467235     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Pregnant ewes were exposed chronically to thermoneutral (TN; 20+/-2 degrees C, 30% relative humidity; n=8) or hyperthermic (HT; 40+/-2 degrees C 12 h/day, 35+/-2 degrees C 12 h/day, 30% relative humidity, n=6) environments between days 37 and 93 of pregnancy. Ewes were killed following 56 days of exposure to either environment (days in treatment (dit)), corresponding to 93+/-1 day post coitus (dpc). Maternal core body temperatures (CBT) in HT ewes were significantly elevated above the TN ewes (HT; 39.86+/-0.1 degrees C vs TN; 39.20+/-0.1 degrees C; P<0.001). Both groups of animals displayed circadian CBT, though HT ewes had elevated amplitudes (HT; 0.181+/-0.002 degrees C vs TN; 0.091+/-0.002 degrees C; P<0.001) and increased phase shift constants (HT; 2100 h vs TN; 1800 h; P<0.001). Ewes exposed to chronic heat stress had significantly reduced progesterone and ovine placental lactogen (oPL) concentrations from 72 and 62 dpc respectively (P<0.05), corresponding to approximately 30 dit. However, when compared with the TN ewes, HT cotyledonary tissue oPL mRNA and protein concentrations were not significantly different (P>0.1). Prolactin concentrations rose immediately upon entry into the HT environment, reaching concentrations approximately four times that of TN ewes, a level maintained throughout the study (HT; 216.31+/-32.82 vs TN; 54. 40+/-10.0; P<0.0001). Despite similar feed intakes and euglycemia in both groups of ewes, HT fetal body weights were significantly reduced when compared with TN fetuses (HT; 514.6+/-48.7 vs TN; 703. 4+/-44.8; P<0.05), while placental weights (HT; 363.6+/-63.3 vs TN; 571.2+/-95.9) were not significantly affected by 56 days of heat exposure. Furthermore, the relationship between body weight and fetal length, the ponderal index, was significantly reduced in HT fetuses (HT; 3.01+/-0.13 vs TN; 3.57+/-0.18; P<0.05). HT fetal liver weights were also significantly reduced (HT; 27.31+/-4.73 vs TN; 45.16+/-6.16; P<0.05) and as a result, the brain/liver weight ratio was increased. This study demonstrates that chronic heat exposure lowers circulating placental hormone concentrations. The observation that PL mRNA and protein contents are similar across the two treatments, suggests that reduced hormone concentrations are the result of impaired trophoblast cell development, specifically trophoblast migration. Furthermore, the impact of heat exposure during maximal placental growth is great enough to restrict early fetal development, even before the fetal maximal growth phase (100 dpc-term). These data highlight that intrauterine growth retardation (IUGR) may result primarily from placental trophoblast cell dysfunction, and secondarily from later reduced placental size.
Authors:
T R Regnault; R J Orbus; F C Battaglia; R B Wilkening; R V Anthony
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of endocrinology     Volume:  162     ISSN:  0022-0795     ISO Abbreviation:  J. Endocrinol.     Publication Date:  1999 Sep 
Date Detail:
Created Date:  1999-11-05     Completed Date:  1999-11-05     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0375363     Medline TA:  J Endocrinol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  433-42     Citation Subset:  IM    
Affiliation:
Perinatal Research Facility, Department of Pediatrics, Division of Perinatal Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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MeSH Terms
Descriptor/Qualifier:
Animals
Arteries
Birth Weight
Female
Gestational Age
Hot Temperature / adverse effects*
Liver / embryology
Organ Size
Placenta / metabolism*
Placental Hormones / blood*
Placental Insufficiency / blood,  metabolism*
Placental Lactogen / blood
Pregnancy
Progesterone / blood
Prolactin / blood
Sheep
Trophoblasts / metabolism
Grant Support
ID/Acronym/Agency:
P01 HD20761/HD/NICHD NIH HHS
Chemical
Reg. No./Substance:
0/Placental Hormones; 57-83-0/Progesterone; 9002-62-4/Prolactin; 9035-54-5/Placental Lactogen

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