The differential effects of glucocorticoid on tissue and plasma amino acid levels

The alteration in free amino acid patterns in various responsive tissues and in plasma has been investigated 4 h after the administration of a relatively low dose of cortisone acetate. In liver, in which cortisone evokes elevated tyrosine transaminase ( L -tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5) levels, a marked depression in the level of tyrosine and an elevation in concentrations of glutamate, aspartate, and alanine are evident. In the liver, in which protein synthesis is augmented under corticoid influences, the concentrations of numerous other amino acids were depressed following cortisone administration. In tissues in which cortisone produces a decrease in protein content, namely, thymus and muscle, the steroid elicited smaller elevations in the concentrations of many amino acids in addition to marked increments in the amounts of glutamate, aspartate, and alanine. Thus the alterations in amino acid patterns in tissues responsive to glucocorticoid seem to be consequent to the hormonally induced elevation of tyrosine α-ketoglutarate transaminase in the liver and to protein loss from lymphoid tissues and muscle.