Steady state maternal-fetal leucine enrichments in normal and intrauterine growth-restricted pregnancies.
The aim of this study was to compare the fetal/maternal (F/M) leucine-enrichment ratio in normal (AGA) and intrauterine growth-restricted (IUGR) pregnancies at the time of fetal blood sampling (FBS). A maternal primed-constant infusion of L-[1-13C]-leucine was given in six AGA and 14 IUGR pregnancies, divided into three groups according to the pulsatility index (PI) of the umbilical artery and to fetal heart rate (FHR): group 1 (normal FHR and PI, four cases); group 2 (normal FHR and abnormal PI, five cases); and group 3 (abnormal FHR and PI, five cases). Maternal arterialized samples were taken at time zero and every 20 min for 125+/-7 min. Umbilical venous samples were obtained after 114+/-42 min of infusion. Under steady state conditions, there was a significant linear relationship between maternal leucine disposal rate and maternal leucine concentration. The comparison of fetal to maternal leucine enrichment showed a progressive dilution of the fetal enrichment relative to the mother between AGA and IUGR of group 1 (0.89 versus 0.78, p < 0.02), group 2 (0.71, p < 0.001), and group 3 (0.62, p < 0.001), and also among the three IUGR groups. The F/M leucine molar percent enrichment (MPE) ratio showed a positive correlation with the umbilical venous oxygen content and an inverse correlation with fetal lactate concentration. We conclude that the dilution in the fetal/maternal leucine-enrichment ratio correlates with the severity of growth restriction and reflects decreased transplacental leucine flux and/or increased protein breakdown within the fetoplacental compartments.
Department of Obstetrics and Gynecology, San Paolo Institute of Biomedical Sciences, University of Milan, Italy.
A M
AM
Marconi
C L
CL
Paolini
L
L
Stramare
I
I
Cetin
P V
PV
Fennessey
G
G
Pardi
F C
FC
Battaglia
D000328:Adult; D002247:Carbon Isotopes; D005260:Female; D005312:Fetal Blood / Q000502:physiology; D005317:Fetal Growth Retardation / Q000378:metabolism*; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006801:Humans; D007262:Infusions, Intravenous; D007930:Leucine / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D008431:Maternal-Fetal Exchange; D010976:Platelet Count; D011247:Pregnancy; D012016:Reference Values; D012044:Regression Analysis; D014469:Umbilical Arteries; D014471:Umbilical Veins
D002247:Carbon Isotopes; D007930:Leucine