Blood amino acids in the pregnant mare and fetus: the effects of maternal fasting and intrafetal insulin.
Abstract: Blood amino acids were measured in twelve chronically catheterized mares and fetuses between 250 and 310 days gestation. The concentrations of the majority of individual amino acids were similar in maternal and fetal arterial blood and no gestational changes were detected. Only methionine, phosphoserine, 3-methyl-histidine and glutamine were consistently higher in the fetus than the mare, whilst certain other amino acids were higher in the maternal blood. Fasting the mares for 36 h led to significant falls in plasma glucose and rises in urea and maternal free fatty acids (FFA). Small but significant decreases in a few amino acids were seen in both fetus and mother, with an overall amino acid fall of 15% in the fetus and 13% in the mare. Virtually all amino acids had risen to basal values by 6 h after feeding. Intrafetal insulin (1 i.u./kg I.V.) as a bolus caused a more dramatic fall in fetal glucose than fasting, with no change in the mare. There were also rapid decreases in many amino acids by 30 min post-insulin and by 2 h all but five amino acids had fallen significantly. There was a drop in total fetal blood amino acids of 29%. These findings show that, in contrast to most other species studied, there is no overall feto-maternal gradient in blood amino acids in the mare, and that fasting leads to small falls in amino acid concentration, whereas intrafetal insulin induces a severe hypoglycaemia with dramatic decreases in almost all amino acids and no change in urea, suggesting a direct anabolic effect of insulin on fetal tissues.
Publication Date: 1994-05-01 PubMed ID: 8074855DOI: 10.1113/expphysiol.1994.sp003777Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This study investigates how maternal fasting and intrafetal insulin affect blood amino acids in pregnant horses and their fetuses. The results illustrate similar blood amino acid concentrations in mares and fetuses, with some exceptions, and reveal that fasting and insulin injections can significantly alter these levels.
Research Methodology
- The researchers conducted the study with twelve chronically catheterized mares and their fetuses between 250 and 310 days of gestation.
- They measured the blood amino acids in both the mares and fetuses, monitoring any potential gestational changes.
- The mares underwent a fasting period of 36 hours, followed by the scientists measuring the effect on plasma glucose and blood amino acids.
- Additionally, the fetuses received insulin injections and their blood was studied for glucose and amino acids.
Key Findings
- The concentrations of most individual amino acids were similar in maternal and fetal arterial blood. Only methionine, phosphoserine, 3-methyl-histidine, and glutamine were found consistently higher in the fetus, while some other amino acids were higher in the maternal blood.
- Fasting led to significant decreases in plasma glucose and slight decreases in some amino acids in both fetus and mother, with an overall amino acid reduction of 15% in the fetus and 13% in the mare. However, within 6 hours of feeding, nearly all amino acids had returned to their original levels.
- Insulin injections in the fetus resulted in a sharper glucose decrease than fasting, with no change in the mares. Thirty minutes post-insulin administration, many amino acids decreased rapidly, and by two hours, all but five had fallen significantly.
Conclusion and Implications
- The study found that there is no overall difference in blood amino acids between the mare and fetus, in contrast to most other studied species.
- Fasting led to small decreases in amino acid concentration, indicating that the nutritional status of the mare can affect fetal blood composition.
- Insulin injections produced a severe drop in glucose and dramatic decreases in almost all amino acids, suggesting insulin has a direct impact on fetal tissues’ metabolism.
- The findings of this study could potentially help better understand the metabolic changes during pregnancy and fasting, guiding strategies to enhance fetal health in equine species.
Cite This Article
APA
Silver M, Fowden AL, Taylor PM, Knox J, Hill CM.
(1994).
Blood amino acids in the pregnant mare and fetus: the effects of maternal fasting and intrafetal insulin.
Exp Physiol, 79(3), 423-433.
https://doi.org/10.1113/expphysiol.1994.sp003777 Publication
Researcher Affiliations
- Physiological Laboratory, Cambridge.
MeSH Terms
- Amino Acids / blood
- Animals
- Fasting
- Female
- Fetal Blood
- Fetus
- Horses / blood
- Hypoglycemia / blood
- Hypoglycemia / chemically induced
- Injections
- Insulin / pharmacology
- Osmolar Concentration
- Pregnancy
- Pregnancy, Animal / blood
- Time Factors
Citations
This article has been cited 3 times.- Martinez RE, Leatherwood JL, Bradbery AN, Paris BL, Hammer CJ, Kelley D, Bazer FW, Wu G. Evaluation of dietary arginine supplementation to increase placental nutrient transporters in aged mares. Transl Anim Sci 2023 Jan;7(1):txad058.
- Manso Filho HC, Costa HE, Wu G, McKeever KH, Watford M. Equine placenta expresses glutamine synthetase. Vet Res Commun 2009 Feb;33(2):175-82.
- Fowden AL, Taylor PM, White KL, Forhead AJ. Ontogenic and nutritionally induced changes in fetal metabolism in the horse. J Physiol 2000 Oct 1;528 Pt 1(Pt 1):209-19.
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