Effect of Oxygen Deprivation on the Metabolism of Fetal and Adult Tissues

Abstract

Fetal liver slices have a remarkably high rate of lipogenesis anaerobically as well as aerobically, shown by the incorporation of carbon-14 from pyruvate into lipids. In contrast, slices of adult or 1-day-old liver have a much lower lipogenetic rate anaerobically than aerobically. Fractionation of the fetal liver lipids showed that phospholipid and glyceride fatty acids are synthesized at essentially equal rates aerobically and anaerobically but cholesterol synthesis is much slower in nitrogen than in oxygen. Fetal liver slices have a respiratory quotient of about 1.5, further evidence of rapid lipogenesis. Lactate production by fetal liver is 90% greater in nitrogen than in oxygen; that of adult liver is only 30% greater. Fetal liver metabolizes anaerobically much more pyruvate carbonyl carbon to carbon dioxide than adult liver does. Direct evidence from the rate of conversion of labeled glucose to labeled pyruvate showed that the glycolytic enzymes of fetal liver respond to anaerobiosis more effectively than those of adult liver. Thus the aging of fetal tissue to adult includes a loss of a) the high rate of glycogen deposition, b) the high rate of activity of one or more glycolytic enzymes which are rate-limiting in the adult, and c) the high rate of lipogenesis which is evident anaerobically as well as aerobically.

Effect of Maternal Oxygen Inhalation on the Fetus with Growth Retardation

“…No improvement in rates of lipogenesis in the IUGR fetus was found when maternal oxygen concentration was increased. This lack of effect of maternal oxygen supplementation on lipogenesis is consistent with studies by Villee and coworkers (21,22). They demonstrated that the effect of total oxygen deprivation on fktal lipogenesis varied with gestational age.…”

Lipid metabolism in the newborn heart.

“…Since the classical investigations of Needham on the metabolism of the developing chick embryo (24), considerable evidence has accumulated that suggests that carbohydrates are the major source of energy for immature organs (4,5). That this obtains in the heart is supported by the presence of higher levels of cardiac glycogen during fetal and neonatal growth than in adult life (25,26), and higher rates of activity in the newborn heart of some enzymes involved in carbohydrate metabolism (27).…”

“…For the tissues of the mammalian fetus, however, carbohydrates rather than lipids appear to serve as the primary source of energy (4,5). This difference in energy metabolism related to maturation suggested that the heart of the newborn, in contrast to that of the adult, might be unable to utilize long chain fatty acids and perforce must rely on glucose as the major substrate for energy production.…”

Glucose Utilization of Cardiac and Skeletal Muscle Homogenates from Fetal and Adult Rhesus Monkesy

“…However, proteins are probably used for synthesis rather than for oxidation in the fetus. Villee et al [38] demonstrated that fetal liver slices do oxidize some radioactive fat to 14 CO 2 although their data were not quantitative. One group studying intact fetuses [33] measured umbilical arterial-venous differences of glucose and fructose in lambs (125-135 days gestaticnal age) and concluded that glucose provides cne-half to one-sixth of the metabolic requirements of this preparation.…”

“…The comment has frequently been made that the mammalian fetus develops in a chronically hypoxic environment [38]. However, how the growing fetus with a low oxygen consumption can perform synthetic processes at a rapid rate is difficult to understand.…”