Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/27594
Citations
Scopus Web of ScienceĀ® Altmetric
?
?
Type: Journal article
Title: Restriction of placental growth results in greater hypotensive response to ?- adrenergic blockade in fetal sheep during late gestation
Author: Danielson, L.
McMillen, I.
Wright, J.
Morrison, J.
Citation: Journal of Physiology-London, 2005; 563(2):611-620
Publisher: Blackwell Publishing Ltd
Issue Date: 2005
ISSN: 0022-3751
1469-7793
Abstract: Placental insufficiency resulting in restriction of fetal substrate supply and fetal hypoxaemia is a major cause of restricted fetal growth and increased neonatal morbidity. Fetal adaptations to placental restriction (PR) include increases in circulating catecholamines and cortisol and decreased fetal body growth, with relative sparing of brain growth. The mechanisms underlying the redistribution of fetal cardiac output in PR fetuses are not known and the aim of this study was to determine whether maintenance of fetal blood pressure (BP) in the PR fetus is dependent on alpha-adrenergic stimulation. PR was induced by removing the majority of uterine caruncles in the ewe before conception. Sterile vascular surgery was performed on seven PR and six control fetuses at 113-120 days' gestation (term = 150 +/- 3 days). Fetuses with a mean arterial PO2 < 17 mmHg between 123 and 127 days' gestation were defined as hypoxic. There was a greater fall (P < 0.05) in fetal BP during phentolamine infusion (i.v: 5 mg bolus, 0.2 mg kg(-1) min(-1) for 2 h) in the hypoxic PR group (-15 +/- 2 mmHg) compared with normoxic controls (-5 +/- 1 mmHg). The fall in fetal BP during phentolamine infusion was directly related to the level of fetal PO2. Fetal BP and HR responses to phenylephrine (i.v.: 40 microg kg(-1)) were not different between PR and control fetuses. The maintenance of BP in the chronically hypoxic fetus is therefore dependent on alpha-adrenergic activation, and this fetal adaptation to a suboptimal intrauterine environment pre-dates the development of significant growth restriction. While this adaptation may play a critical role in the redistribution of fetal cardiac output to ensure the sparing of brain growth, it may have adverse consequences for peripheral vascular function in the neonatal period and in adult life.
Keywords: Placenta; Animals; Sheep; Placental Insufficiency; Phenylephrine; Phentolamine; Adrenergic alpha-Agonists; Adrenergic alpha-Antagonists; Pregnancy; Blood Pressure; Time Factors; Female; Fetal Hypoxia
RMID: 0020051961
DOI: 10.1113/jphysiol.2004.080523
Appears in Collections:Molecular and Biomedical Science publications

Files in This Item:
There are no files associated with this item.


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.