Fig. 4. Assessment of whole-body protein kinetics. Both labeled (from outside of the body via plasma) and unlabeled amino acids (AAs) cross the cell membrane in proportion to their relative concentrations (i.e., tracer-to-tracee ratio) to enter the free intracellular AA precursor pool (i.e., Rd1). Once inside cells, the tracer can be oxidized (or hydroxylated in the case of Phe, Rd3) or incorporated into protein (Rd2). In a physiological steady state, Ra1 reflects the rate of protein breakdown and is equal to Rd1. This figure was created with BioRender.com.
Rd = rate of disappearance; Ra = rate of appearance; Leu = leucine; Phe = phenylalanine.
© 2022 Ann Clin Nutr Metab
