Blood amino acids in the pregnant mare and fetus: the effects of maternal fasting and intrafetal insulin

Silver, M.; Fowden, AL; Taylor, PM; Knox, Jean; Hill, CM

doi:10.1113/expphysiol.1994.sp003777

Cited by 24 publications

(17 citation statements)

References 10 publications

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“…The increment in maternal plasma glucagon during fasting was not related to gestational age (r = −0·55, n = 5, P > 0·05), the actual maternal glucose concentrations at the end of the fast (r = 0·102, n = 5, P > 0·05) or to the decrement in maternal plasma glucose during fasting (r = −0·018, n = 5, P > 0·05). In common with previous findings (Silver et al 1994), fasting for 36 h had no effect on fetal or maternal á_amino nitrogen concentrations (data not shown). discussion The present findings indicate that the pancreatic á cells of the fetal foal are functional and responsive in utero during late gestation.…”

Section: Fastingsupporting

confidence: 92%

Pancreatic α Cell Function in the Fetal Foal During Late Gestation

Fowden

Forhead

Bloomfield

et al. 1999

Experimental Physiology

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summaryPlasma glucagon concentrations were measured in chronically catheterized fetal ponies and their mothers between 260 days of gestation and term ( 335 days). Fetal á cell responses to arginine and variations in fetal glycaemia were also examined during late gestation. Immunoreactive glucagon was present in fetal plasma at 260 days of gestation and its concentration in utero increased after 320 days and then again at birth. Maternal plasma glucagon concentrations were higher after 300 days than earlier in gestation but were lower than the corresponding fetal value throughout the period of gestation studied. Fetal á cells responded rapidly to intravenous arginine infusion but not to changes in the fetal glucose level induced by maternal fasting for 36 h or by intrafetal infusion of glucose. The maximal increment in fetal plasma glucagon in response to arginine occurred at the end of the 5 min infusion and was positively correlated to the basal preinfusion plasma glucagon concentrations. Fetal plasma glucagon concentrations were unaffected by either hyper-or hypoglycaemia. In contrast, maternal plasma glucagon levels were significantly increased by fasting. These observations indicate that equine pancreatic á

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Section: Fastingsupporting

confidence: 92%

Pancreatic α Cell Function in the Fetal Foal During Late Gestation

Fowden

Forhead

Bloomfield

et al. 1999

Experimental Physiology

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“…Similarly, there is little evidence for significant fructose oxidation by the uteroplacental tissues in either the pregnant sheep or horse (Silver, 1981;Meznarich et al 1987;McGowan et al 1995). Amino acids also appear to be less readily available as metabolic substrates in the uteroplacental tissues of the horse than sheep during late gestation (Carter et al 1991;Silver et al 1994;Chung et al 1998). Lipids, on the other hand, appear to be more plentiful in the horse than sheep.…”

Section: Discussionmentioning

confidence: 99%

Equine Uteroplacental Metabolism at Mid‐ and Late Gestation

Fowden¹,

Forhead²,

White³

et al. 2000

Experimental Physiology

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Uptakes of oxygen, glucose and lactate by the gravid uterus, fetus and uteroplacental tissues were measured in chronically catheterized pregnant ponies and their fetuses at mid‐ and late gestation (term 335 days). Rates of O2 uptake by the gravid uterus, fetus and uteroplacental tissues were significant at both gestational ages and were 2‐ to 3‐fold higher in late gestation than the mid‐gestation values of 3338 ± 794, 1352 ± 258 and 2035 ± 602 μmol min‐1, respectively (n = 4). Similarly, there were significant uptakes of glucose by the gravid uterus, fetus and uteroplacental tissues at both mid‐ and late gestation. However, unlike O2 uptake, glucose uptake by the uterus and uteroplacental tissues did not increase between mid‐ and late gestation. No significant uptakes or outputs of lactate were observed by the uterus or uteroplacental tissues at either gestational age, although there was a significant umbilical uptake of lactate in late but not mid‐gestation. There was no change in the distribution of uterine O2 uptake between the fetus and uteroplacental tissues with increasing gestational age. The uteroplacental tissues accounted for about 50% of the uterine O2 uptake at both gestational ages. In contrast, the proportion of the uterine glucose uptake used by the uteroplacental tissues decreased from 73.2 ± 2.1% (n = 5) at mid‐gestation to 61.1 ± 1.9% (n = 4, P < 0.02) in late gestation. The gestational changes in uteroplacental carbohydrate metabolism in the mare differ from those seen in the ewe and may have important consequences for the duration and outcome of pregnancy in the mare.

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“…It has been reported, however, that in the fetal horse only a few plasma amino acids are present at higher concentrations than in the maternal plasma but, although such measurements are limited, they do indicate that glutamine is concentrated in the equine fetus (Silver et al 1994;Zicker et al 1994;Pere 2003). Glutamine is the most abundant free alpha amino acid in the circulation of most mammals (Curthoys and Watford 1995;Newsholme et al 2003) and it plays important roles in the transport of nitrogen, carbon and energy between tissues, including a large uptake across the placenta during pregnancy.…”

Section: Introductionmentioning

confidence: 94%

Equine placenta expresses glutamine synthetase

Manso

Costa

et al. 2008

Vet Res Commun

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In most mammalian species the developing fetus utilizes large amounts of glutamine derived both from the maternal circulation and synthesized de novo in the placenta. The present study was designed to determine the role of the placenta in glutamine synthesis in the horse. The placentae from eight Standardbred mares were sampled immediately after parturition together with additional tissues obtained at necropsy from three Standbred mares during diestrous. Glutamine synthetase protein was detectable in the non-pregnant horn of the placenta in amounts similar to those seen in gluteus muscle, but the amount in the pregnant horn was two times greater than in the non-pregnant horn. Glutamine was the second most abundant amino acid in amniotic fluid at a concentration of 310 +/- 26 micromole/L with that of glycine being 535 +/- 48 micromole/L. The most abundant amino acids in placental tissue were glycine (3,732 +/- 194 micromole/Kg), glutamate (3,500 +/- 343 micromole/Kg) and glutamine (2,836 +/- 208 micromole/Kg). The results illustrate the importance of glutamine to the equine fetus and establish that the placenta, particularly the pregnant horn, has considerable capacity for glutamine synthesis.

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Blood amino acids in the pregnant mare and fetus: the effects of maternal fasting and intrafetal insulin

Cited by 24 publications

References 10 publications

Pancreatic α Cell Function in the Fetal Foal During Late Gestation

Pancreatic α Cell Function in the Fetal Foal During Late Gestation

Equine Uteroplacental Metabolism at Mid‐ and Late Gestation

Equine placenta expresses glutamine synthetase

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