ALTERATION IN MAGNITUDE OF INDUCTION OF TYROSINE TRANSAMINASE BY GLUCOCORTICOIDS .2. EFFECTS OF PHENOBARBITAL O P' DDD AND DIETHYLAMINOETHYL DIPHENYLPROPYLACETATE (SKF 525A) ON METABOLISM OF TRIAMCINOLONE ACETONIDE

Treatment of rats with phenobarbital or o,p′DDD diminishes and treatment with SKF 525A augments the increase in hepatic 2.6.1.5, l-tyrosine-2-oxoglutarate amino-transferase (tyrosine transaminase) by triamcinolone acetonide (TrA). In addition, phenobarbital decreases and SKF 525A increases, in the liver and blood, the concentration of radioactivity derived from (3H-labeled TrA (3H-TrA). The transformation of 3H-TrA into polar metabolite(s) by 9000 g liver supernate was found to be NADPH and O2 dependent. This transformation is stimulated by treating the rats with either phenobarbital or o,p′DDD and inhibited by treatment with SKF 525A. Moreover, the in vitro addition of SKF 525A strongly inhibits this reaction. It is proposed that the effects of phenobarbital, o,p′DDD and SKF 525A on the magnitude of increase of tyrosine transaminase by TrA is related to the alteration in the rate of metabolism of TrA. © 1969.