AJP - Endocrinology and Metabolism, Vol 271, Issue 1 E186-E191, Copyright © 1996 by American Physiological Society
Fetal substrate uptake during increased ovine fetal cortisol concentration
J. R. Milley
Department of Pediatrics, University of Utah School of Medicine, Salt Lake City 84132, USA.
Corticosteroid administration adversely affects fetal growth and
consequently, unless metabolic rate increases (thereby increasing the need
for fetal metabolic substrates), reduces fetal need for exogenous
substrates. To find whether the uptake of all or only certain metabolic
substrates was affected by fetal hypercortisolemia, we measured exogenous
uptake of glucose, lactate, and alpha-amino nitrogen during fetal
hypercortisolemia in seven late-gestation sheep fetuses. Hydrocortisone
infusion increased fetal cortisol concentrations from normal to values
usually associated with late gestation (4.3 +/- 0.9 vs. 72.5 +/- 5.0 ng/ml;
P < 0.001). In association with increased fetal cortisol concentration,
both fetal metabolic rate and the uptakes of glucose and lactate remained
constant. However, the uptake of alpha-amino nitrogen-containing substances
fell (39.6 +/- 3.1 vs. 28.5 +/- 3.4 mumol.kg-1.min-1; P < 0.002) as did
the proportion of metabolic rate (0.45 +/- 0.04 vs. 0.32 +/- 0.04; P <
0.002) that could be supported by metabolism of these substances. The
proportion of fetal metabolic rate that could be supported by complete
metabolism of all substrates taken up across the placenta decreased (1.09
+/- 0.07 vs. 0.95 +/- 0.06; P < 0.02). In conclusion, hypercortisolemia
alters the composition of oxidative substrates taken up by the sheep fetus
and decreases total fetal substrate uptake. These changes occur within
hours of exposure to increased cortisol concentration.
