The Rate of Amino Acid Nitrogen and Total Nitrogen Accumulation in the Fetal Lamb 1

Abstract

Abstract

Total body water and nitrogen concentrations were determined for whole body homogenates of 18 fetal lambs. Nitrogen concentration averaged 10.5 ± 0.1 mg nitrogen/100 mg dry tissue. Amino acid represented approximately 82% of the total nitrogen and 55% of the total carbon content of the fetus. The carbon/nitrogen ratio attributable to amino acids decreased from 3.42 at 66 days to 3.06 at term. Total amino acid concentrations in the whole body homogenates were also determined for 20 amino acids. Cystine and hydroxy-proline concentrations increased significantly (correl. coeff. = 0.78) and markedly with gestation. The branch chain amino acids, leucine, isoleucine, and valine, along with phenylalanine, showed a significant decline in concentration (correl. coeff. ≧ −0.79). From these rates of amino acid and nitrogen accretion the adequacy of the exogenous supply of amino acids and nitrogen to the fetus via the umbilical uptake can be assessed. Calculations of the excess supply of amino acids to the fetus above their rates of accretion are presented for the fetal lamb during late gestation.