Glucose partitioning in the pregnant ewe: Effects of undernutrition and exercise

Abstract

~Maternal whole-body glucose entry rate and uterine and umbilical net uptakes of glucose and oxygen were measured in single-pregnant ewes which were either well-fed throughout, or fed at 0.3-0 4 predicted energy requirement for 7-21 d during late pregnancy. All ewes were studied while standing at rest and then while walking on a treadmill at 0.7 m/s on a 10" slope for 60 min. Underfed ewes suffered significant decreases in live weight and had lower fetal, but not placental, weights at 140-144 d gestation. Undernutrition also caused large decreases in maternal glycaemia and glucose entry rate, which were associated with equally large decreases in uterine and umbilical net uptakes and 0, quotients of glucose, and with a decrease in placental glucose transfer capacity. Exercise caused increases in maternal blood concentration, entry rate and uterine net uptake of glucose, the magnitudes of which were not significantly affected by plane of nutrition. Umbilical glucose uptake and placental glucose transfer capacity increased during exercise in underfed but not fed ewes. The fractional distribution of maternal glucose to the pregnant uterus, and of uterine glucose uptake to the fetus, were unaltered by undernutrition; during exercise, a disproportionately small fraction of the increased maternal glucose supply went to the uterus. The results confirm that the ovine conceptus responds to nutritional reduction in maternal glucose availability in a manner similar to non-uterine maternal tissues. Major reductions in glucose supply appear to override putative glucose-sparing mechanisms which may operate to favour the conceptus in better-nourished animals. Glucose: Pregnancy: Uterus: Fetus: SheepIt is well-established that the growing sheep conceptus makes substantial demands on the maternal glucose supply, especially in late pregnancy. At this time the gravid uterus may account for about 30 50 % of whole-body glucose utilization in well-fed, monotocous ewes (Hay et al. 1983;Oddy et al. 1985). However, there is conflicting evidence on the degree to which uterine glucose consumption is responsive to changes in maternal supply. On the one hand, the findings of Oddy et LEI. (1985) appear to support the long-held notion (e.g. Barcroft, 1946) that when maternal glucose production is limited by undernutrition, the unmodified demands of the conceptus take priority over those of maternal tissues. On the other, studies by Hay et al. (1983, 1984b) strongly suggest that fetal and utero-placental uptake of maternal glucose is attenuated in proportion with the reduction of maternal supply during short-term starvation.Therefore, in the present study we re-investigated the effects of undernutrition during late pregnancy on the partitioning of maternal glucose between the pregnant uterus and nonuterine maternal tissues and, within the uterus, between fetal and utero-placental tissues. In the same animals we also examined uterine and fetal responses to an acute perturbation of maternal glucose metabolism, achieved by treadmill exercise. Res...

Dietary melatonin supplementation alters uteroplacental amino acid flux during intrauterine growth restriction in ewes

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The influence of extruding corn grain in diets fed to Finn × Awassi crossbred ewes during late pregnancy on birth weight of lambs

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