Net placental transfer of free amino acids against varying concentrations

Hill, Penny M. M.; Young, Maureen

doi:10.1113/jphysiol.1973.sp010393

Cited by 89 publications

(24 citation statements)

References 23 publications

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“…The plasma amino acid values in the pregnant ewe were lower than in the non pregnant sheep (LEIBHOLZ [20]) s might be expected from the fall in total <%-amino nitrogen observed by CURET et al [4] during gestation in the ewe. The general pattern and level of the amino acid concentrations in the maternal plasma were similar to that found in the human subject (YouNG and PRENTON [40]) and in the guinea pig (HiLL and YOUNG [12]); the high glycine is characteristic of other ruminants, while the branched chain amino acids, valine, isoleucine and leucine are low in comparison with the cow and the goat (VERBEKE and PEETERS [35], MEPHAM and LINZELL [26]). LEIBHOLZ'S [21] finding of l and 3 methylhistine in the sheep plasma was confirmed for both mother and fetus.…”

Section: Discussionsupporting

confidence: 74%

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Young¹,

Fadyen²

1973

Journal of Perinatal Medicine

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Section: Discussionsupporting

confidence: 74%

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Young¹,

Fadyen²

1973

Journal of Perinatal Medicine

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“…Differences in radioac-UTILIZATION OF METABOLITES BY RAT FETUS 9 tivity between left and right fetuses for 14C-glucose, I4C-glycerol, and I4C-alanine after maternal infusion through the left uterine artery with the respective uniformly I4C-labeled tracers, and the magnitude of these differences (the larger corresponding to I4C-alanine and the smaller to 14C-glycerol) are in agreement with the way it is known they cross the placenta (10,27,28). Plasmaspecific activities of the respective tracers in fetuses from the left uterine side were also significantly higher than in those from the right ones, indicating that the infused tracer directly reached fetuses from the left side whereas it reached those from the right side after its dilution in maternal circulation.…”

Section: Discussionsupporting

confidence: 70%

Lactate Production and Absence of Gluconeogenesis from Placental Transferred Substrates in Fetuses from Fed and 48-H Starved Rats

1987

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ABSTRACf. Fed and 48-h starved rats were infused on absent and develops only after birth (5-8) as a consequence of day 21.5 of gestation for 20 min through the left uterine the induction of cytosolic phosphoenolpyruvate carboxykinase artery with [U-14C-]-~-glucose, [U-"C]-glycerol, or 9). Due to the conversion of administered [l-14C]-glycerol to -L-alanine. The mother and fetuses from both uterine horns I4C-glucose (10) it has been proposed that the gluconeogenetic were processed separately for radioactivity measurements pathway is functional in the rat fetus above the triose phosphate in plasma and liver. Differences in radioactivity values step, but in other studies gluconeogenesis from glycerol was not between fetuses from the left and the right sides are used detected in in vitro (1 1) or in vivo (12) rat fetus preparations.as indexes of placental transference of the infused tracers Maternal fasting has been reported to induce gluconeogenesis prior to their distribution and transformation in the mater-prematurely in the rat fetus (13-15), but this finding has not nal circulation. After infusion of [U-14Cj-~-glucose, [U-I4Cj been consistent and no change in fetal liver gluconeogenic activ--glycerol, or [U-14CJ-~-alanine, plasma radioactivity values ities were reported after 48 h of maternal fasting (16). In addition, and specific activities corresponding to the respective in-no changes were detected in fetal liver lipogenic enzymes after fused tracer appeared much higher in fetuses from the left maternal fasting (16) whereas fetal lipogenesis from 3H20 was than the right uterine side. Plasma I4C-lactate values also inhibited (1 7). In order to clarify these controversies, the present were higher in the left than the right fetuses indicating study was performed to determine the comparative in vivo metthat fetoplacental structures produced lactate from those abolic fate of D-glucose, L-alanine, and glycerol in fetuses from placentally transferred 14C-metabolites. No difference in fed and 48-h starved late pregnant rats. Labeled substrates were plasma '4C-glucose between left and right uterine horn infused through the maternal left uterine artery according to our fetuses was observed after maternal infusion with either recently described technique (18) for placental transfer studies [U-14C]-glycerol or [U-14Cj-~-alanine, either in fed or 48-h which allows determination of the metabolic fate of substrates in starved rats. In the mother both [U-14q-glycerol and [U-the rat fetus independently of interconversions occumng in the I4q-L-alanine were efficiently converted to I4C-glucose, mother. and this process was significantly enhanced with starvation. I4C-fatty acids present in fetal liver after maternal infusions with either [U-14Cj-~-glucose or [U-'4C]-glycerol were de-METHODS creased by starvation whereas no fatty acid synthesis from wistar female rats, mated when weighing 170-190 g, were [U-14C1-L-a1anine was detected-Much less '4C-g1~ceride studied at day 21.5 of gestation (estimated by the appearance of glycer...

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“…In the case of amino acids, the main method of transport is by an active process, and the metabolism of the placenta is crucial to the control of any distortion of the maternal aminogram. The placenta con centrates a large number of amino acids from the maternal blood [6] but the regula tion of placental amino acid transport is influenced by maternal, placental and fetal variables [7,8]. In our study, the maternal increase in glutamine and ornithine, which were not infused, probably represents the result of an acute overload of the amino acid disposal system.…”

Section: Discussionmentioning

confidence: 72%

Effect on the Fetus of Infusing a Commercial Amino Acid Preparation into a Pregnant Sheep

MacMahon

Frampton²,

Yardley³

1990

Neonatology

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The common clinical practice of intravenous feeding of the pregnant woman poses the question of the effect on the fetus of such infusions. We have used the sheep as a model to study the change in fetal amino acid levels after a maternal infusion of Synthamin 13. The maternal plasma aminogram largely reflects the amino acid pattern in the infusate. However, in the fetal circulation only the branched chain amino acids (leucine, isoleucine and valine), phenylalanine and alanine rose significantly after infusion. Only leucine and isoleucine were observed to spill into the fetal urine. The results suggest that the ovine placenta selectively modifies the amino acid profile presented to the fetus when the maternal plasma aminogram is distorted. However, the fetus is not totally protected from changes in phenylalanine, which in high concentrations, is detrimental to normal development.

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Net placental transfer of free amino acids against varying concentrations

Cited by 89 publications

References 23 publications

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Lactate Production and Absence of Gluconeogenesis from Placental Transferred Substrates in Fetuses from Fed and 48-H Starved Rats

Effect on the Fetus of Infusing a Commercial Amino Acid Preparation into a Pregnant Sheep

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