Abstract
ABSTRACT: In vivo substrate utilization has not been described for the maturing fetal lung. We, therefore, studied pulmonary delivery and use of major fetal substrates in six chronically catheterized fetal lambs over 119–141 days gestation. Oxygen, glucose, lactate, and α-amino nitrogen concentrations were measured in the pulmonary artery and pulmonary vein whereas lung blood flow was determined using labeled microspheres. We found that lung oxygen availability and use increased near term. Oxygen delivery averaged 4960 ± 480 (SEM) μl/min and rose with fetal age (p < 0.05); uptake averaged 708 ±111 μl/min and increased 93% near term (p < 0.05). In contrast, glucose availability and use fell with gestation. Pulmonary artery glucose decreased with time (p < 0.001), with a mean drop of 5.05 ± 1.71 mg/dl in individual animals (p < 0.05). Average glucose uptake was 844 ± 225 μg/min and fell near term (p < 0.05). Lactate was produced by the lung at a mean rate of 534 ±176 μg/min; this did not change with gestation. Lung amino nitrogen availability increased with fetal age. Pulmonary artery amino nitrogen rose by 1.35 mg/dl, or 43% (p < 0.001) and lung delivery of amino nitrogen increased (p < 0.05). The mean pulmonary glucose/O2 ratio was 1.48 ± 0.26 and decreased with gestation (p < 0.05), being < 1.0 near term. The glucose-lactate/O2 ratio was 0.67 ± 0.26, implying that 30% of lung oxidative metabolism is still unaccounted for. The alterations in delivery of substrates to the lung which were identified may serve as signals for pulmonary maturation, inducing the changes in lung metabolism that were found near term.
Similar content being viewed by others
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Simmons, R., Charlton, V. Substrate Utilization by the Fetal Sheep Lung during the Last Trimester. Pediatr Res 23, 606–611 (1988). https://doi.org/10.1203/00006450-198806000-00016
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1203/00006450-198806000-00016