Origin and Metabolic Fate of Plasma Glycerol in the Rat and Rabbit Fetus

Gilbert, Marc

doi:10.1203/00006450-197702000-00002

Cited by 21 publications

(10 citation statements)

References 12 publications

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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%

“…,./ Thiq conclusion is in agreement with reports based on different methodologies (5)(6)(7)(8) but is in contradiction with results of other studies (10,13,15), most of which ( 1 3, 15) used 4-day rather than 2-day starvation periods indicating that fetal gluconeogenesis is only induced after prolonged maternal food deprivation. In one study, in which the rat diet was not specified (lo), gluconeogenesis from labeled glycerol was detected in the fetuses, but the tracer was injected into the fetus when exteriorized from the uterus.…”

Section: Discussioncontrasting

confidence: 56%

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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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Section: Discussionsupporting

confidence: 70%

Section: Discussioncontrasting

confidence: 56%

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

1987

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“…According to Levitsky et al [41], gluconeogenesis from lactate occurs in the baboon foetus during the last quarter of pregnancy in the maternal fed and fasted states. On the contrary, endogenous production of glucose by the foetal foal [33], the foetal pig [34], or the foetal rat [42] is negligible in the fed state. However, increased glycogenic capacity towards term, related to the prepartum rise in endogenous cortisol, was demonstrated in the foetal foal [43], sheep [40], and pig [44].…”

Section: Glucosementioning

confidence: 96%

Materno-foetal exchanges and utilisation of nutrients by the foetus: comparison between species

Père

2003

Reprod. Nutr. Dev.

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-Several general features of nutrient uptake and utilisation by foetuses are similar among mammalian species. Nevertheless, there are also differences linked mainly to differences in placental permeability. Glucose and lactate are the main energetic substrates of the foetus. In normal conditions, the oxidation of carbohydrates accounts for about 75, 60 and 50% of oxygen uptake in the foetal pig, foal and lamb, respectively, and acetate accounts for about 10% in ruminants. Acidic amino acids are synthesised by the foetus, whereas neutral and basic amino acids are transported from the placenta. As shown by the high urea level in foetal blood, amino acids are partly involved in the oxidative metabolism of foetuses; their contribution is higher in ruminants than in humans, horses and pigs. Fatty acids cross the haemochorial placenta of rodents, rabbits and primates, and are incorporated into the foetal lipids, whereas their uptake by ruminant, pig and horse foetuses is very low.materno-foetal exchange / mammal / carbohydrate / fatty acid / amino acid

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“…It should be pointed out that during the marked drop in maternal plasma level there was no concomitant change in foetal plasma level therefore suggesting a poor placental transfer of glycerol. In rat and rabbit placenta, transfer of glycerol has been demonstrated by intravascular injection of [ 14 C]glycerol to the mother in late pregnancy [23].…”

Section: Glycerolmentioning

confidence: 99%

“…Due to technical difficulties, these studies were undertaken in species in which the females carry foetuses of large size and which are also less prone to abortion such as the cow [8] and sheep [28,29]. Some information has also been gained in smaller species like rabbits [24], guinea pigs [57,58] or rats [23], using labelled substrates. The conclusions which were drawn from these studies do not however necessarily apply to the foetal pig because of its lower fatness at birth and the different placenta.…”

Section: Introductionmentioning

confidence: 99%

Effects of meal intake on materno-foetal exchanges of energetic substrates in the pig

Père

2001

Reprod. Nutr. Dev.

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-Catheters were implanted in 18 gilts at 99 days of pregnancy to study the effects of meal intake on uterine and umbilical uptake of energetic substrates in the conscious pig. Blood samples were withdrawn at 105 days of pregnancy from 10 min before and up to 90 min after feeding of a 2.5-kg meal. Plasma glucose was 2.2 to 2.5 times lower and blood lactate 2 to 3 times higher in the foetus than in the sow. Glucose and lactate increased after the meal. Their umbilical uptake amounted to 0.32 and 0.26 mmol . L -1 , respectively. Fructose was found in large amounts in foetal plasma (4.3 mmol . L -1 ), but it did not seem to be metabolised by the foetus. Meal intake decreased plasma levels of FFA and glycerol in the sows, whereas they increased in the foetuses. A small FFA and glycerol umbilical uptake was recorded (14 and 6 µmol . L -1 , respectively). Most features of the maternofoetal exchanges in the porcine species resemble those of other species, especially ruminants. materno-foetal exchange / energetic substrate / meal intake / pig Résumé -Effets de la prise alimentaire sur les échanges materno-foetaux de substrats énergétiques chez le porc. Des cathéters ont été implantés sur 18 truies à 99 jours de gestation afin d'étudier chez l'animal vigile les effets d'une prise alimentaire sur la capture de substrats énergétiques par l'utérus et le foetus. Des échantillons de sang ont été prélevés à 105 jours de gestation entre 10 min avant et 90 min après la distribution d'un repas de 2,5 kg. La glycémie était 2,2 à 2,5 fois plus faible et la lactatémie 2 à 3 fois plus élevée chez le foetus que chez la mère. Elles augmentaient après le repas. La capture de glucose et de lactate par le foetus était respectivement de 0,32 et 0,26 mmol . L -1 . Les concentrations sanguines de fructose étaient élevées chez le foetus (4,3 mmol . L -1 ), mais ce substrat ne semblait pas métabolisé. La consommation du repas provoquait une diminution des teneurs plasmatiques en AGL et en glycérol des truies alors qu'elles augmentaient chez les foetus. Une faible Reprod. Nutr. Dev. 41 (2001) 285-296 285

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Origin and Metabolic Fate of Plasma Glycerol in the Rat and Rabbit Fetus

Abstract: Pediat. Res. 11: 95 -99 (1977) Fetus glycerol

Cited by 21 publications

References 12 publications

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

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

Materno-foetal exchanges and utilisation of nutrients by the foetus: comparison between species

Effects of meal intake on materno-foetal exchanges of energetic substrates in the pig

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