Disappearance of palmitic acid from plasma of fetal and newborn sheep.
These studies were undertaken to measure the kinetic constants that characterize the disappearance of a representative free fatty acid (FFA) from the plasma of fetal and newborn sheep. A bolus of albumin-complexed [14C]palmitic acid was infused intravenously, and during the next 8 min, 24 arterial samples were collected to characterize the disappearance curve. Palmitic acid disappearance from plasma was well described by a double-exponential model. When birth was simulated in utero, kinetic values were not changed by cooling. However, after intrauterine ventilation with O2, the volume of distribution of the FFA increased 29%, its plasma clearance rate decreased 26%, and its apparent half-life in the plasma lengthened from 0.8 to 1.2 min (all P < 0.01, n = 8). After umbilical cord occlusion, plasma clearance rate decreased a further 19% and half-life lengthened to 1.4 min. About 60% of the increase in FFA concentration during simulated birth is explained by increased release from adipose stores, and 40% is explained by decreased clearance. Further experiments tested the influence of FFA concentrations themselves. After infusion of unlabeled FFA, clearance of the tracer decreased 23% (P < 0.05, n = 5), a result consistent with a saturable membrane transporter of FFAs.
Power
G G
GG
Division of Perinatal Biology, Loma Linda University School of Medicine, California 92350.
Yoneyama
Y
Y
Asakura
H
H
Sawa
R
R
D000818:Animals; D000831:Animals, Newborn / Q000097:blood*; D001784:Blood Gas Analysis; D003080:Cold Temperature; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000493:pharmacokinetics; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006207:Half-Life; D006454:Hemoglobins / Q000378:metabolism; D007743:Labor, Obstetric / Q000502:physiology; D010100:Oxygen / Q000494:pharmacology; D010169:Palmitic Acids / Q000097:blood* / Q000493:pharmacokinetics; D011247:Pregnancy; D012756:Sheep; D014470:Umbilical Cord / Q000502:physiology
D005230:Fatty Acids, Nonesterified; D006454:Hemoglobins; D010169:Palmitic Acids; D010100:Oxygen