Responses of fetal sheep to reduced maternal renal blood flow and
maternal hypertension.
Lumbers, E. R., J. H. Burrell, A. D. Stevens & C. Bernasconi.
School of Physiology and Pharmacology, University of New South
Wales, Sydney, 2052, Australia
APStracts 3:0207R, 1996.
The effects on 16 chronically catheterised fetal sheep of reducing and
restoring maternal renal blood flow (RBF) and thus inducing and
reversing hypertension in uninephrectomised pregnant ewes were
studied; controls were 3 fetuses carried by uninephrectomised ewes in
which RBF was not reduced and which did not become hypertensive.
Within 24-72h of maternal RBF reduction fetal arterial PO2 had fallen
(P <0.001) and PCO2 had increased (P< 0.025) ; fetal
arterial pressure also increased (P<0.005). These effects
persisted despite restoration of maternal RBF and reversal of
maternal hypertension. Within 24-72h of reducing maternal RBF, fetal
urine flow had increased (P< 0.005), it remained elevated over
the first 3h after RBF was restored; 24-72h later it was lower
(P<0.025) and back to control levels. The excretion of sodium,
potassium and chloride showed a similar increase when maternal RBF
was reduced (P< 0.001) with return to control values 24-72h
after RBF had been restored. Fetal glomerular filtration rate did not
change, thus the natriuresis and diuresis that occurred was due to
reduced tubular solute and water reabsorption (P< 0.025). These
changes in fetal renal function may be related, in part, to changes
in fetal PO2 and PCO2 but they are most likely due to reduced
maternal renal function due to the restriction in maternal RBF as
they were reversed when RBF was restored.
Received 1 November 1995; accepted in final form 29 May 1996.
APS Manuscript Number R679-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96