Figure 3
From: The application of 2H2O to measure skeletal muscle protein synthesis
Theoretical prediction model based on fractional synthetic rate (FSR) measurements made over 24 h. The fraction of new alanine (f) synthesized in mixed muscle of fish (epaxial myomere), rats (mixed gastrocnemius) and humans (vastus lateralis), and a hypothetical protein that has a rapid renewal rate (protein "x"). As a result of skeletal muscle having a slow renewal rate, calculating a FSR with the traditional precursor:product labeling equation provides a reliable estimate (i.e., there is no significant difference in the values when using rise-to-plateau kinetics, Ft). However, when proteins have a rapid renewal rate (e.g., protein "x"), the affect of long sampling intervals begins to have substantial effects on estimates of FSR. Thus, it is recommended that the labeling protocol be either reduced or multiple samples be collected with calculations made using F t = fmax × (1-e-kt).