Effect of infusion of a protein hydrolysate on blood cell amino acid distributions

¹ Department of Biological Chemistry, Harvard Medical School, and the Fifth Surgical Service (Harvard), Boston City Hospital, Boston, Massachusetts

The relationships between the concentrations of unbound amino acids in the plasma and erythrocytes, together with amino acid utilization, are studied during the intravenous infusion of a protein hydrolysate in adults. Concentrations of alanine, proline, tyrosine, histidine, valine, phenalanine, leucine plus isoleucine, and urea increase in both the plasma and the erythrocytes. Lysine and methionine concentrations change much less in the erythrocytes than in the plasma. Ornithine and serine plus glycine concentrations in the erythrocytes do not change. It is concluded that amino acids with hydrophobic groups equilibrate readily whereas glycine and amino acids which contain charged or hydroxyl groups equilibrate poorly across the erythrocyte membrane. The changes in glutamine and alanine concentrations during and after infusion suggest that the infused amount of these two amino acids is less than optimum. An expression for amino acid uptake is given.