Abstract

The relative rate of synthesis of glutamic-alanine transaminase (GAT) in rat liver was measured at various times after the administration of massive doses of prednisolone sodium phosphate or hydrocortisone succinate by the L-leucine-¹⁴C pulse-labeling method. The rate of synthesis was unchanged 3.5 hr after the administration of prednisolone and 6.5 hr after the administration of hydrocortisone. However, the rate was increased approximately 2-fold after 6.5 hr of prednisolone administration, and approximately 3-fold after 2 days of prednisolone or 5 days of hydrocortisone. Thus, the first noticeable increase in the GAT synthesis, occurring some 6 hr after the hormone administration, lags behind those of glutamic-tyrosine transaminase (GTT) and tryptophan pyrrolase (TP) which have been shown to occur within 3 hr after an administration of hormone. This observation indicates that the stimulatory effect of glucocorticoid hormone on the synthesis of liver proteins are sequential rather than simultaneous.