Comparative aspects of fetal carbohydrate metabolism

Nutrient transfer across the equine placenta: correlation of structure and function

“…The transplacental gradient can be abolished in the ewe by fetal infusion or hypoxic stresses and the fetus then supplies the placenta with glucose. The transfer normally operates downhill, but is capable of transferring radioactively labelled glucose in either direction after maternal or fetal injection, illustrating the dynamic nature, flexibility and complexity of the system (Hay 1995;Fowden 1997). Such findings also indicate that there may be a considerable 'pool' of glucose available for placental metabolism but not for transport.…”

“…This is directed far more to the fetal than the maternal circulation. There is no transplacental transfer from the mother (Fowden 1997). In the human placenta there are different isoforms on apical and basal syncytiotrophoblast membranes (Settle et al 2004), but no localisations have as yet been reported for the placenta of the horse or ruminant.…”

“…This is an overall gradient down which the glucose molecule must travel, but in practice it covers 8 individual membrane steps, each of which may or may not have a unique concentration of a particular carrier isoform with individual kinetic properties. Also, a large proportion, up to 70% but variable between species, of the glucose taken up by the placenta is utilised by placental tissues for growth and maintainance of function, thereby complicating estimates of the rate of transport from mother to fetus (Fowden 1997). Little is known about the factors regulating the activity of this complex transport system.…”

Energetic metabolic profile of ewes presenting low body condition score induced to subclinical hypocalcemia in early postpartum

“…The highest concentrations were observed at the first postpartum day, and it can be attributed to cortisol actions. This hormone gradually increases five days before delivery, and allows greater circulating glucose availability; thus, it influences the action of glucose carrier GLUT4 in peripheral tissues, as well as stimulates hepatic gluconeogenesis (Bassett 1963, Fowden 1997, Ingvartsen and Andersen 2000. The results contradict the reports of Schlumbohm and Harmeyer (2003), who showed the hindering effect of hypocalcemia on glucose turnover.…”

Fetal programming for athletic performance in the horse: potential effects of IUGR

“…Another potential influence on normal growth and development is the finding that the fetal foal deaminates little amino acid and has limited glucogenic capacity (Fowden 1997); it is, therefore, more dependent on transplacental supply of glucose than other species studied. Further, the rates of umbilical uptake and uteroplacental consumption of glucose are relatively high, the gravid uterus accounting for 70% of the maternal rate of glucose utilisation in late gestation (Evans 1971).…”