Amino acid concentrations in fetal and maternal plasma

Glendening, Mary Beth; Margolis, Alan J.; Page, Ernest W.

doi:10.1016/s0002-9378(15)33674-7

Cited by 59 publications

(21 citation statements)

References 9 publications

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“…Our data for L-methionine, L-leucine, and L-ornithine, taken together with considerable other data from a number of laboratories [3,4,8,9,11,17,21,22], is compatible with the hypothesis that, in general, amino acids are transferred from mother to fetus by a process of active transport, i.e., carrier-mediated, saturable, energy-dependent, stereospecific, and operating against a chemical gradient.…”

Section: Discussionsupporting

confidence: 88%

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Transfer of Cyst(e)ine and Methionine across the Human Placenta

et al. 1973

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ExtractAfter intravenous loads in pregnant women, L-methionine, L-leucine, and L-ornithine were transferred from maternal to fetal plasma against a two-to threefold difference in initial concentration. Cyst(e)ine is unique among the free amino acids of plasma in that its basal concentration in maternal plasma was equal to or greater than that in fetal plasma. Furthermore, after intravenous loads with L-cystine or L-cysteine, total cyst(e)ine (cystine and cysteine) was transferred less readily to the fetal plasma. Although the concentrations of cystine in the fetal plasma continued to rise in the face of rapidly falling concentrations of cystine in the maternal plasma, at no time during the experiment did the concentration of cystine in fetal plasma exceed that in the maternal plasma. When D-cystine was administered intravenously to a mother, in amounts equimolar with L-cystine, the transfer of D-cystine was not measurable. SpeculationCyst(e)ine is the end-product of the transsulfuration pathway, which transfers the sulfur from the 4-carbon skeleton of methionine to the 3-carbon skeleton of serine. Methionine-activating enzyme, the first enzyme on this pathway, is inhibited by cyst(e)ine [2,5,20]. It is also allosteric [19], a characteristic often associated with negative feedback inhibition. Cystathionase, which cleaves cystathionine to cysteine and a-ketobutyrate and is the last enzyme on this pathway, is absent from the liver and brain of the human fetus. Therefore, we postulate that the special mechanism for the transfer of cyst(e)ine across the human placenta is an adaptation to control the transfer of sufficient maternal cyst(e)ine for synthesis of protein and glutathionine without undue inhibition of the activation of methionine to iS'-adenosylmethionine, a compound involved in important synthetic reactions.

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Section: Discussionsupporting

confidence: 88%

“…The general observation of the higher concentration of amino acids in fetal plasma had been made in a number of laboratories [8,11,18,21,22]. That cysteine was an exception was previously unappreciated.…”

Section: Resultsmentioning

confidence: 99%

Transfer of Cyst(e)ine and Methionine across the Human Placenta

et al. 1973

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“…The C: M ratios for taurine, lysine and arginine are considerably higher at full-term pregnancy in the human than in the rhesus monkey [3,11,12,17]. An explanation for these differences is not apparent, but with these exceptions, the C: M ratios demonstrated by the rhesus monkey at full-term pregnancy are similar to those reported for the human.…”

Section: Discussionmentioning

confidence: 73%

“…Numerous studies have demonstrated that each amino acid is maintained at higher levels in fetal blood than in maternal blood [3,4,7,9,11,12,17,20,26]. This has occurred even in the face of an elevation in the level of amino acid in maternal blood (4,13,15].…”

Section: Discussionmentioning

confidence: 99%

The Free Amino Acids of Serum During Development of Macaca mulatto II. During Pregnancy and Fetal Life

Kerr

1968

Pediatr Res

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The levels of free amino acids of serum have been investigated during pregnancy and fetal life in the rhesus monkey (Macaca mulatta). Samples of venous blood were drawn simultaneously from the mother and the umbilical cord of the fetus at cesarian section delivery performed at exactly 50, 75, 100, 125, and 150 days conceptual age and at full-term vaginal delivery (168+4 days). Although a wide range of values was found for each amino acid at each age studied (tables I and II), certain trends were evident. All levels of maternal amino acids except those for taurine, lysine, 3-GH 3 -histidine and arginine were lower at full-term pregnancy than they were in nonpregnant adult animals. This pattern was apparent by 75 days of gestation and was maintained without further change during the remainder of pregnancy.The sum of the individual values of all free amino acids in fetal blood was highest at 75 days of gestation; this resulted primarily from elevated levels of glutamine and glutamic acid, histidine, methionine, and valine. Levels of 3-GH 3 -histidine and glycine showed the opposite trend and were higher during late pregnancy than at 75 days of fetal age. The levels of the other amino acids did not undergo significant changes throughout gestation.At each age studied, the level of each amino acid in fetal blood was higher than that of the corresponding level in maternal blood. The umbilical cord: maternal ratios for alanine, glutamine plus glutamic acid, leucine, 3-GH 3 -histidine and valine were significantly elevated at the earliest gestational age. The mean cord: maternal value for all amino acids studied showed a progressive decrease with increasing fetal maturity.

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“…The knowledge of the nature and control of this transport system is important in order to understand the correlation with fetal nutri tion and growth, in particular if we consider that each tissue concentrates amino acids dif ferently, and that the availability along with the increased uptake of amino acids is ac companied by an acceleration of all endocellular reactions related to them [11,15,16].…”

Section: Discussionmentioning

confidence: 99%

Levels of Total and Free Tryptophan in Maternal and in Umbilical Blood of Infants Born by Vaginal Delivery and by Elective Cesarean Section

Zanardo¹,

Casson²,

Costa

et al. 1985

Neonatology

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The variations of total and free tryptophan levels in samples of maternal and umbilical blood obtained on the occasion of elective cesarean section have been compared with similar samples taken from vaginal deliveries. In the neonates studied the umbilical blood levels of total and free tryptophan have been found to be higher than in the blood of the respective mothers, while the percentage of free tryptophan is comparable. In addition, the umbilical blood levels of both fractions of tryptophan appeared to be higher in newborn infants after spontaneous delivery than in those after elective cesarean section. These data show an active transport of tryptophan through the placental barrier that seems to be favored by spontaneous delivery.

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Amino acid concentrations in fetal and maternal plasma

Cited by 59 publications

References 9 publications

Transfer of Cyst(e)ine and Methionine across the Human Placenta

Transfer of Cyst(e)ine and Methionine across the Human Placenta

The Free Amino Acids of Serum During Development of Macaca mulatto II. During Pregnancy and Fetal Life

Levels of Total and Free Tryptophan in Maternal and in Umbilical Blood of Infants Born by Vaginal Delivery and by Elective Cesarean Section

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