Protein synthesis in ovine muscle and skin: sequential measurements with three different amino acids based on the large-dose procedure.

1. Protein synthesis has been determined in biopsies from ovine skin and muscle by sequential use of three [13C] amino acids, valine leucine and phenylalanine, as large-dose injections. 2. Leucine and phenylalanine increased plasma insulin concentrations within 40 min of injection. 3. All three amino acids decreased the plasma concentrations of other amino acids. 4. Intracellular free amino acids in muscle decreased while those in skin increased. 5. The fractional rates of protein synthesis were similar, regardless of which amino acid was used, although the rates for muscle were significantly less than for skin (2.1 vs 11.0%/day, P < 0.001).