OVINE FETAL METABOLISM DURING NOREPINEPHRINE INFUSION

Although stress in fetal life not only increases fetal catecholamine c oncentration but also decreases fetal growth, there have been few stud ies that define the specific role of catecholamines in mediating the f etal response to stress. None, however, have investigated effects on f etal amino acid or protein metabolism, processes that should be affect ed during aberrant fetal growth. Therefore, hormone concentrations as well as oxygen, glucose, lactate, and amino nitrogen, leucine? and pro tein metabolism were measured with and without norepinephrine infusion in fetuses of eight pregnant eu es (118-125 days of gestation). Trans umbilical uptake of oxygen increased during norepinephrine infusion, w hereas uptake of glucose remained constant and that of lactate and ami no 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 oxi dative metabolism and therefore that fetal growth was diminished. Both fetal leucine uptake and oxidation decreased during norepinephrine in fusion, as did fetal protein synthesis and proteolysis. Fetal protein synthesis fell more than proteolysis, however. Consequently, fetal pro tein accretion! a variable closely related to fetal growth, also fell. Thus the effects of norepinephrine infusion in fetuses suggest that f etal catecholamines play an important role not only in altering fetal metabolism but also in regulating fetal growth.