Glucose, lactate and oxygen metabolism in the fetal pig during late gestation

Abstract

SUMMARYUsing [U-_4C]glucose tracer, rates of umbilical uptake, utilization and production of glucose, and of CO2 production from glucose carbon, were measured in seven chronically catheterized fetal pigs, when the sow was in the fed state, between 100 and 113 days of gestation (term, 114 + 2 days). At the same time, rates of umbilical 02 and lactate uptake were determined in all seven fetuses by the Fick principle. The mean fetal rates of umbilical glucose uptake, glucose utilization and CO2 production from glucose carbon were 38.4 + 4.2, 41-3 + 5.2 and 126-9 + 12-6 #smol min-' (kg fetal body weight)-', respectively (n = 7). No glucose production was therefore detected in the fetuses. Production of CO2 from glucose carbon accounted for 37-3 + 3.4% (n =7) of the umbilical 02 uptake, which averaged 340 + 13 jumol min-kg-' (n = 7). There was also significant umbilical lactate uptake in the fetal piglets when the sow was in the fed state (32.6 + 10-4 #tsmol min-1 kg-', n = 7, P <0-05). No significant changes in fetal glucose, 0°or lactate metabolism were observed with increasing age towards term. The fetal rates of glucose metabolism and of umbilical uptake of 02 and lactate were not correlated with the fetal blood glucose level. Hence, glucose is used for both oxidative and tfOn-oxidative metabolism in utero and is an important, although not the sole, source of carbon for metabolic processes in the fetal pig during late gestation.

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

“…If completely oxidised, it would then account for 10-15% of the umbilical O 2 uptake. Recent results from Fowden et al [34] on fed sows show that the contribution of lactate should be higher in pigs than in other species, since its umbilical uptake represents about 85% that of glucose, and if completely oxidised, 20-30% of the umbilical O 2 uptake.…”

“…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].…”

“…The oxidation rate of glucose carbon has been measured in several species by using labelled glucose. Glucose accounts for a higher proportion of oxygen consumption in the foetal foal (about 40% [33]) or foetal pig (35-40% [34]) than in the foetal lamb (about 30% [35][36][37]) during late gestation. In the case of maternal hypoglycaemia induced by fasting, the contribution of exogenous glucose to foetal requirements is reduced to approximately half of the normal value in sheep [30], its foetal utilisation is decreased, and foetal gluconeogenesis is increased [15,38].…”

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

“…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. To our knowledge, the studies undertaken in pigs allow to gain access to the metabolism of the pregnant uterus, but excepted Fowden et al [21], they do not give any information about the foetal metabolism. A chronic catheterisation method has been developed to allow the study of nutrition and metabolism in conscious and unstressed pig foetus [38].…”

Maternal and Fetal Carbohydrate, Lipid and Protein Metabolisms

“…Although uterine, placental and fetal glucose uptakes are related to maternal glucose concentrations, the distribution of uterine glucose uptake to fetal and uteroplacental glucose uptakes is regulated by fetal glucose concentrations independent of the maternal glucose levels (20). The rates of umblical uptake and utilization of glocose did not change with gestational age when they were evaluated on a weight specific basis in piglets (24). A fetus uses 55 kcal/kg/day based on calculation of fetal oxygen consumption (25).…”