Figure 1
From: The application of 2H2O to measure skeletal muscle protein synthesis
Fundamental principal of the precursor:product labeling method to determine muscle protein synthesis. Traditionally, a labeled (tracer) and unlabeled (tracee) amino acid are provided either as a primed-continuous infusion or flooding dose, and mix with the protein-free amino acid pool in the blood. If the fate of the amino acid is incorporation into muscle protein, then entry into the cell is facilitated by amino acid transporters prior to charging an aminoacyl-tRNA. When using 2H2O, the 2H rapidly equilibrates with body water and labels amino acids (e.g., alanine) intracellularly via transamination reactions (e.g., alanine aminotransferase), which can then charge aminoacyl-tRNA and become incorporated into growing peptides.