Ovine fetal metabolism during norepinephrine infusion. Milley, J. Ross. Division of Neonatology, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, Utah 84132
APStracts 4:0106E, 1997.
Although stress in fetal life not only increases fetal catecholamine concentration but also decreases fetal growth, there have been few studies that define the specific role of catecholamines in mediating the fetal response to stress. None, however, have investigated effects on fetal amino acid or protein metabolism, processes that should be affected during aberrant fetal growth. Therefore, hormone concentrations as well as oxygen, glucose, lactate, and amino nitrogen, leucine, and protein metabolism were measured with and without norepinephrine infusion_ in fetuses of eight pregnant ewes (118-125 d gestation). Transumbilical uptake of oxygen increased during norepinephrine infusion while uptake of glucose remained constant and that of lactate and amino acids fell. The proportion of fetal oxidative metabolism that could be supported by transplacental uptake of exogenous substrates was < 1, indicating that endogenous substrates were used to maintain fetal oxidative metabolism, and, therefore, that fetal growth was diminished. Both fetal leucine uptake and oxidation decreased during norepinephrine infusion, as did fetal protein synthesis and proteolysis. Fetal protein synthesis fell more than proteolysis, however. Consequently, fetal protein accretion, a variable closely related to fetal growth, also fell. Thus, the effects of norepinephrine infusion in fetuses suggest that fetal catecholamines not only play an important role in altering fetal metabolism, but also in regulating fetal growth. 

Received 12 February 1997; accepted in final form 22 April 1997.
APS Manuscript Number E66-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 13 May 1997