Free fatty acid metabolism in fetal and newborn sheep

Abstract

The metabolism of free fatty acids (FFA) was studied in the term ewe, sheep fetus and newborn lamb. The concentration of FFA is about 10 times greater and the concentration of triglyceride fatty acids (TGFA) 2 1/2 times greater in maternal than in fetal plasma. After intravascular administration of palmitic acid-1-C14 complexed to homologous albumin, the initial rates of disappearance of FFA radioactivity from maternal and fetal circulations were similar, with half-times of approximately 2 minutes. Radioactivity appeared in the opposite circulation as FFA indicating that the syndesmochorial placenta is permeable to palmitic acid. Survival of the newborn lamb is associated with a fivefold increase in plasma concentration of FFA and no significant change in glucose or fructose during the first 30 minutes after birth. Failure to survive is associated with lack of increase in plasma FFA concentrations, while glucose concentrations do not differ from those found in surviving lambs. These data suggest that sympathetic nervous system activity is responsible for the FFA elevation and that increased activity of the sympathetic nervous system or FFA mobilization is closely related to survival of the newborn lamb.

Plasma Fatty Acid Profile of Gestating Ewes Supplemented with Fishmeal

“…It appeared that, in contrast with the nonruminant, the ruminant placenta was relatively impermeable to 18:2n6 and 18:3n3 (Hansen et al, 1964;Leat, 1966). In addition, it has been shown that the placentas of rats, rabbits and sheep are relatively impermeable to plasma cholesterol and phospholipids, whereas plasma non-esterified FA can pass the placental barrier into the fetus (Duyne et al, 1960;Popjak, 1954;McBride and Korn, 1964). Leat (1966) reported that sow-plasma non-esterified FA contained 4.8-10:0 times more 18:2n6 than ruminants and suggested that less 18:2n6 acid would pass into the ruminant fetus than into the non-ruminant fetus in this way.…”

The Metabolism of Subcutaneous Adipose Tissue in the Immediate Postnatal Period of Human Neonates. III. Role of Fetal Glycogen in Lipolysis and Fatty Acid Esterification in the First Hours of Life

“…Dynamics of lipolysis studies in vitro in adipose tissue from neonates show that lipolysis increases rapidly from the moment of birth, reaches its maximum within a few hours, and then gradually decreases [22,25]. The biochemical mechanism of elevated lipid mobilization in human neonates is not known exactly [29,40], but in newborn lambs activity of the sympathetic nervous system is increased at this time [38]. The basal release of glycerol from adipose cell suspensions has been found to be higher in the first hours of extrauterine life than at any other time during the first 10 days of life, yet response to norepinephrine was less [23,25].…”

In Vitro Metabolism of Palmitic Acid in Human Fetal Tissue

“…that, as in sheep [26], guinea pig [7,10], rabbit [25], rat Injection of labeled palmitic acid parenterally to the […”