Effect of puromycin on insulin-stimulated amino-acid transport in muscle.

Abstract

INSULIN stimulates both the transport1,2 of amino-acids and their incorporation3 into protein in skeletal muscle. Previous attempts to associate these two effects have failed4–7. That is, inhibition of new protein synthesis by puromycin did not impair the stimulatory effect of insulin on amino-acid transport. It was therefore concluded that the stimulation of amino-acid transport by insulin did not depend on the synthesis of new protein. Recent studies have shown that the transport of neutral amino-acids in embryonic bone8, foetal calvarium (G. A. Finerman, S. J. Downing and L. E. Rosenberg, unpublished results), diaphragm9 and kidney cortex10 was impaired by puromycin or cycloheximide when 2 h of incubation8 or preincubation9,10 with these antibiotics preceded the uptake study. Because previous experiments with insulin and puromycin in diaphragm muscle did not measure amino-acid uptake after such intervals of preincubation with puromycin, we carried out experiments to reinvestigate the effect of prolonged inhibition of protein synthesis on the stimulation by insulin of amino-acid transport in muscle.