Some aspects of foetal and uteroplacental metabolism in cows with indwelling umbilical and uterine vascular catheters.

Abstract

SUMMARY1. The experiments were carried out on conscious pregnant Jersey cows with intravascular catheters implanted during late gestation in umbilical and uterine vessels. All but three of fifteen animals delivered live healthy calves.2. Routine daily analyses were made of blood gas tensions, pH and packed cell volume in foetal and maternal blood; plasma concentrations of glucose, fructose, lactate and urea were also determined. Measurements of plasma free fatty acids and blood acetate concentrations were made less frequently. Foetal heart rate and arterial blood pressure were recorded in animals with an umbilical arterial catheter.3. The concentration differences between foetal and maternal blood or plasma in glucose, urea and acetate were measured in fifteen animals. The maternal-to-foetal glucose and acetate gradients across the placenta were high while the foetal-to-maternal plasma urea differences were small.4. In those animals with patent arterial and venous catheters, uterine and umbilical blood flows were measured together with the arteriovenous differences in 02, glucose, acetate and lactate so that rates of foetal and uterine consumption could be estimated. The rates of utilization of 02, glucose and acetate by the foetus were lower than the values for the whole uterus, while the uteroplacental metabolism of these substrates was very high.5. Significant amounts of lactate, which appeared to be produced by the uteroplacental tissue, were utilized by the foetus; the remainder passed into the uterine venous blood.6. The total substrate/02 quotient for the foetus, calculated from the utilization of known metabolites, appeared to be greater than 1. Thus, in the calf some carbon accumulation from sources other than amino acids, the uptake of which was not measured, would seem to occur. These results R. S. COMLINE AND M. SILVER and the metabolic activity of the uterine tissues are discussed in relation to comparable findings in the sheep.

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

“…L -1 ; Burd et al [6]), and cows (0.10 mmol . L -1 ; Comline and Silver [8]). As in ruminants, it seems reasonable to assume that foetal metabolism also relies on foetal lactate [27].…”

“…This could be partly explained by a lack of knowledge regarding the transfer of nutrients from the mother to the foetus, as well as the control of foetal nutrient utilisation. Due to technical difficulties, these studies were undertaken in species in which the females carry foetuses of large size and which are also less prone to abortion such as the cow [8] and sheep [28,29]. Some information has also been gained in smaller species like rabbits [24], guinea pigs [57,58] or rats [23], using labelled substrates.…”

Reducing Equivalent Shuttles in Developing Porcine Myocardium: Enhanced Capacity in the Newborn Heart

“…Even at incrcased workloads, the proportion of ATP produced via fatty acid oxidation remained stable (38). The mechanism of substrate preference has not been determined, although it may relate to increased levels of lactate and decreased levels of fatty acids circulating in the fetus (40,41) or a reduction in carnitine acyltransferase I activity in newborn heart (42). This enzyme is needed to allow mitochondria to use long-chain fatty acids.…”

Cellular Expression of the Monocarboxylate Transporter (MCT) Family in the Placenta of Mice

“…However, there is strong evidence of net lactate uptake and consumption by ovine and bovine fetuses as a whole [2,6,32,33]. Lactate and other monocarboxylates not only serve the major carbon sources for fatty acid synthesis but also are utilized as a metabolic energy source in various fetal tissues, such as the porcine heart [34], rat brain [35], and ovine liver [36].…”