On the kinetics of turnover of serum albumin

Abstract

1. 1. The isotope concentrations of serum albumin were determined (a) after feeding of 1- 14C-glycine and 1- 13C-glycine at a 5 day interval and (b) after transfusion of plasma doubly labeled with both 14C and 13C glycine. From the difference of the isotope concentration changes in the two animals, exchange of glycine residues in serum albumin could be excluded. 2. 2. The isotope concentrations of individual amino acids of serum albumin were determined (a) after feeding of a mixture of 14C amino acids (b) after transfusion of multiple labeled plasma and (c) after continuous administration of a mixture of labeled amino acids. It was found that partition of albumin between the intra- and extra-vascular fluids and re-utilization of labeled amino acids arising through the breakdown of body proteins can account for the particular kinetics observed under different conditions. Reutilization of labeled amino acids also accounts for the deviation from the expected first order kinetics for the rates of change of isotope concentration.