Abstract
The successful chronic catheterization of sheep fetuses at midgestation (approx. 75 days) has permitted us to investigate the fractionation of leucine metabolism during early fetal life, with comparisons of similar measurements made by us at later stages of gestation.
Twelve pregnant ewes with gestations of 73-88 days were studied after 3-5 days of recovery from surgery for placement of catheters in the umbilical vein and artery, uterine vein, maternal artery and fetal peripheral vein. Uterine and umbilical blood flows were determined with the steady-state diffusion technique following a tritiated water infusion. 14C-leucine was infused into the fetus at a constant rate and after a 2½ hour equilibration period the leucine disposal rate and the leucine flux to CO2 and protein synthesis were calculated, employing a three-compartment model to quantify 14C-leucine flux out of the fetal compartment. The leucine disposal rate within the fetal compartment was 9.16 ± 0.66 (SEM) umole kg−1 min−1. Leucine oxidation measured by 14CO2 production was 3.1 ± 0.57 (SEM) umole kg−1 min−1. while leucine flux into protein was 5.96 ± 0.28 (SEM) umole kg−1 min−1. The calculated fractional protein synthetic rate (Ks) was 0.214 ± 0.009 (SEM), which is significantly higher than that in late gestation fetuses. The importance of amino acids as fetal fuel is underscored by the quantification of a 30% oxidation rate for leucine at this gestational age.
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Kennaugh, J., Bell, A., Meschia, G. et al. 280 ONTOGENETIC CHANGES IN LEUCINE DISPOSAL RATE OXIDATION RATE AND PROTEIN SYNTHETIC RATE DURING FETAL LIFE. Pediatr Res 19, 157 (1985). https://doi.org/10.1203/00006450-198504000-00310
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DOI: https://doi.org/10.1203/00006450-198504000-00310