Stress induced tyrosine aminotransferase activity via glucocorticoid receptor.

Antiglucocorticoid RU486 was used to prove that stress induced tyrosine aminotransferase (TAT) activity is mediated via glucocorticoid receptor (GR) in the rat liver. Oral dose of RU486 (10 mg/kg) occupied liver cytosol GR in 5 min and concomitantly blocked stress (15 min immobilization) induced enzyme activity. Post-stress increase of TAT activity was observed when RU486 was administered 10 min after stress exposure. A minimal increment of 15.2 micrograms/dl plasma corticosterone ("B") lasting for 25 min is necessary for TAT induction. In the intact organism this is the time interval necessary for "B" released by external stimuli to induce synthesis of the enzyme TAT in the rat liver via GR.