The effects of potassium ions and denervation on protein synthesis and the transport of amino acids in muscle.

1. The effects of varying concentrations of K(+) during incubation, of denervation and of various drugs on the accumulation of (14)C-labelled amino acids, their incorporation into protein and the stimulation of these processes by insulin in rat diaphragm preparations were studied. 2. The accumulation of glycine and aminoisobutyrate and incorporation of glycine into protein was less in tissue incubated in K(+)-free buffer or 20mm-K(+) than with 5-10mm-K(+). Incorporation of leucine was unaffected. 3. Incorporation into protein of amino acids by diaphragm that had been denervated 3 days previously was elevated. Accumulation of both glycine and aminoisobutyrate was also raised but that of phenylalanine was unaffected. 4. Accumulation of glycine by diaphragm and extensor digitorum longus muscle was decreased by a number of agents including cocaine and mepyramine. 5. The stimulation of incorporation by insulin was unaffected by changes in K(+) or in the presence of cocaine and mepyramine. Denervated tissue was markedly less responsive to insulin than its control. 6. The results are discussed in the context of the relation of amino acid accumulation to operation of the Na(+) pump and the influence of insulin thereon.