Abstract
The effect of maternal fasting upon fetal nitrogen uptake in the form of free amino acids (QN), fetal oxygen consumption (QO2) glucose utilization (QG), urea excretion (QU) and umbilical blood flow (UBF) was assessed in the chronic fetal lamb preparation. Five animals (mean gestational age 118 days) were studied in the fed state 7 days after surgery and again 12 days post-operatively after 5 days of maternal fasting. QG decreased from 6.88 ± 1.04 to 2.69 ± .30 mg/kg/min during the fasted state while QO2 remained unchanged (7.38 ± .53 vs. 7.41 ± .70 ml/kg/min). The glucose:oxygen quotient thus decreased from .69 to .28 during fasting. QU increased from 448 to 691 mg/kg/day, although nitrogen uptake from the placenta did not change during fasting (802 vs. 768 mg/kg/day). These findings indicate that the fetal metabolic rate remains unchanged during the fasted state while exogenous glucose utilization decreases to <50% of fed state values. An augmented utilization of amino acids is reflected by the increased urea excretion rate, but without a detectable increase in nitrogen uptake from the placenta. Therefore, the ovine fetus becomes increasingly reliant on amino acid substrate during fasting and may be required to catabolize its own protein stores, or to direct exogenous amino acids from growth to catabolism to maintain adequate energy substrate.
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Lemons, J., Schreiner, R., Moorehead, H. et al. 263 INCREASED AMINO ACID CATABOLISM IN THE FETAL LAMB DURING MATERNAL FASTING. Pediatr Res 15 (Suppl 4), 484 (1981). https://doi.org/10.1203/00006450-198104001-00274
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DOI: https://doi.org/10.1203/00006450-198104001-00274