A recent study from our laboratory (7) demonstrated that 5 days after a single im injection of TE (200 mg), FSR and model-derived protein synthesis increased 2-fold, with no change in FBR. Further, in agreement with the present findings, Ferrando et al. (7) demonstrated an increased utilization of intracellular amino acids by showing a strong relationship between protein breakdown and protein synthesis. Although our kinetic data strongly support these findings, the magnitude of the synthetic response with OX was not as great as that with TE. With OX, we found 44% and 28% increases in FSR and model-derived protein synthesis (FO,M), respectively.