Abstract
Conclusions
1. Measurement of venous-arterial differences across the umbilical circulation of the sheep fetus in utero and across the maternal uterine circulation in the chronic animal preparation shows no significant passage of free fatty acids to the fetus. This is true despite relatively high maternal blood free fatty acid concentrations. There is a small venous-arterial difference of glycerol across the umbilical circulation; this is, however, sufficient to account for only a small portion of the fetal oxygen consumption due to substances other than glucose. Free fatty acids and glycerol therefore do not appear to constitute a significant part of the metabolic fuel supplied by the mother to the sheep fetus in utero.
2. The fetuses of fasted ewes show an elevation of blood free fatty acid and glycerol concentrations. Measurements of venous-arterial differences across the umbilical circulation indicate that this free fatty acid and glycerol rise is of fetal origin.
3. Fetal infusion of norepinephrine results in lipolysis in the fetus, as evidenced by elevation of fetal blood free fatty acid and glycerol concentrations.
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