| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
1 Dept of Physiology, University of Cambridge, Cambridge, United Kingdom
2 Physiology, University of Cambridge, United Kingdom
3 ICMS, Hammersmith, United Kingdom
4 Departmental of Physiology, University of Cambridge, Cambridge, United Kingdom
5 Department of Physiology, University of Cambridge, Cambridge, United Kingdom
* To whom correspondence should be addressed. E-mail: dag26{at}cam.ac.uk.
We tested the hypothesis that the fetal cardiovascular responses to hypoxemia change close to term in relation to the prepartum increase in fetal basal cortisol and investigated, in vivo, the neural and endocrine mechanisms underlying these changes. Using 25 chronically instrumented sheep, the fetal heart rate and peripheral hemodynamic responses to 1 hour of hypoxemia were studied within three narrow gestational age ranges: 125-130 days (n = 13), 135-140 (n = 6) and at >140 (n = 6), where term is ca. 145 days. Chemoreflex function and plasma concentrations of vasoconstrictor hormones were measured. Reductions in fetal arterial PO2 during hypoxemia were similar at all age groups. Between 125-130 days, hypoxemia elicited transient bradycardia, femoral vasoconstriction and increases in plasma catecholamines, neuropeptide Y (NPY), vasopressin, ACTH and cortisol concentrations. Close to term, in association with the prepartum increase in fetal basal cortisol, there was a developmental increase in the magnitude and persistence of fetal bradycardia and in the magnitude of the femoral constrictor response to hypoxemia. The mechanisms mediating these changes close to term included increases in the gain of chemoreflex function and in the magnitudes of the fetal NPY and vasopressin responses to hypoxemia. Data combined irrespective of gestational age, revealed significant correlations between fetal basal cortisol and fetal bradycardia, femoral resistance, chemoreflex function and plasma vasopressin concentrations. The data show that the fetal cardiovascular defense to hypoxemia changes in pattern and magnitude just prior to term due to alterations in the gain of the neural and endocrine mechanisms mediating them, in parallel with the prepartum increase in fetal basal cortisol.
This article has been cited by other articles:
|
|
 |
|
  M. Ream, A. M. Ray, R. Chandra, and D. M. Chikaraishi Early fetal hypoxia leads to growth restriction and myocardial thinning Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2008; 295(2): R583 - R595. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Wassink, L. Bennet, L. C. Booth, E. C. Jensen, B. Wibbens, J. M. Dean, and A. J. Gunn The ontogeny of hemodynamic responses to prolonged umbilical cord occlusion in fetal sheep J Appl Physiol, October 1, 2007; 103(4): 1311 - 1317. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Bennet, L. C. Booth, N. Ahmed-Nasef, J. M. Dean, J. Davidson, J. S. Quaedackers, and A. J. Gunn Male disadvantage? Fetal sex and cardiovascular responses to asphyxia in preterm fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2007; 293(3): R1280 - R1286. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Wibbens, L. Bennet, J. A. Westgate, H. H. De Haan, G. Wassink, and A. J. Gunn Preexisting hypoxia is associated with a delayed but more sustained rise in T/QRS ratio during prolonged umbilical cord occlusion in near-term fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2007; 293(3): R1287 - R1293. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
| Visit Other APS Journals Online |
