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Am J Physiol Endocrinol Metab 278: E839-E845, 2000;
0193-1849/00 $5.00
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Vol. 278, Issue 5, E839-E845, May 2000

Effect of dexamethasone on fetal hepatic glutamine-glutamate exchange

Michelle Timmerman1, Cecilia Teng2, Randall B. Wilkening2, Paul Fennessey2, Frederick C. Battaglia2, and Giacomo Meschia2

1 Department of Obstetrics and Gynecology, Erasmus University, 3000 DR Rotterdam, The Netherlands; and 2 Division of Perinatal Medicine, Departments of Pediatrics, Pharmacology, and Physiology, University of Colorado Health Sciences Center, Denver, Colorado 80262

Intravenous infusion of dexamethasone (Dex) in the fetal lamb causes a two- to threefold increase in plasma glutamine and other glucogenic amino acids and a decrease of plasma glutamate to approximately one-third of normal. To explore the underlying mechanisms, hepatic amino acid uptake and conversion of L-[1-13C]glutamine to L-[1-13C]glutamate and 13CO2 were measured in six sheep fetuses before and in the last 2 h of a 26-h Dex infusion. Dex decreased hepatic glutamine and alanine uptakes (P < 0.01) and hepatic glutamate output (P < 0.001). Hepatic outputs of the glutamate (RGlu,Gln) and CO2 formed from plasma glutamine decreased to 21 (P < 0.001) and 53% (P = 0.009) of control, respectively. RGlu,Gln, expressed as a fraction of both outputs, decreased (P < 0.001) from 0.36 ± 0.02 to 0.18 ± 0.04. Hepatic glucose output remained virtually zero throughout the experiment. We conclude that Dex decreases fetal hepatic glutamate output by increasing the routing of glutamate carbon into the citric acid cycle and by decreasing the hepatic uptake of glucogenic amino acids.

fetus; amino acids; fetal liver; placenta


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M. Timmerman, R.B. Wilkening, and T.R.H. Regnault
Induction of Glutamate Dehydrogenase in the Ovine Fetal Liver by Dexamethasone Infusion during Late Gestation
Experimental Biology and Medicine, January 1, 2003; 228(1): 100 - 105.
[Abstract] [Full Text] [PDF]

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 Am. J. Physiol. Endocrinol. Metab.Home page
C. Teng, F. C. Battaglia, G. Meschia, M. R. Narkewicz, and R. B. Wilkening
Fetal hepatic and umbilical uptakes of glucogenic substrates during a glucagon-somatostatin infusion
Am J Physiol Endocrinol Metab, March 1, 2002; 282(3): E542 - E550.
[Abstract] [Full Text] [PDF]


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