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

1. 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. Rountine 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 O2, 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/O2 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 and the metabolic activity of the uterine tissues are discussed in relation to comparable findings in the sheep.