Critical Assessment of Methods Used to Measure Protein Synthesis In Human Subjects

The loss of body protein that frequently accompanies illness occurs through changes in protein synthesis and degradation. In human tissues, rates of protein synthesis can be assessed with stable isotopic tracer techniques and mass spectrometry. The basic principles of these methods are explained, and the advantages and drawbacks of the two main approaches, the constant infusion method and the flooding method, are described. Examples are given of the use of these methods to investigate protein synthesis and surgical trauma, pathologies of the gastrointestinal tract and the response of tumor growth to amino acid supplements.