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Regulation of hepatic tyrosine amino transferase ec

Biochimica et Biophysica Acta 677(3-4): 433-444

Regulation of hepatic tyrosine amino transferase ec

Tyrosine aminotransferase induction was studied in hepatocytes from untreated, partially and fully glucocorticoid[dexamethasone]-induced rats: enzyme activities were initially 12.9 .+-. 1.7 (n = 16), 41.4 .+-. 3.2 (n = 6) and 117.9 .+-. 10.5 (n = 7) mU/mg protein, respectively. Untreated or fully induced hepatocytes maintain initial levels, whereas partially induced hepatocytes increase their tyrosine aminotransferase activity even in the presence of actinomycin D. Fully induced hepatocytes possess a normal protein synthesizing machinery and the mechanisms to degrade selectively tyrosine aminotransferase. The effect of progesterone treatment is consistent with these cells retaining a high dexamethasone level. Glucagon induces tyrosine aminotransferase via its 2nd messenger, cAMP. This induction decreases dramatically with in vivo glucocorticoid treatment. Time courses and effects of inhibitors are consistent with these in vivo and in vitro treatments being alternative methods of inducing tyrosine aminotransferase by the same basic pretranslational step.

Accession: 006288430

Related references

Galabov G.P., 1972: Participation of the central nervous system in the regulation of rat liver tyrosine amino transferase activity evidence for the existence of 2 tyrosine amino transferase messenger rna with different life time. Dokladi Na B"lgarskata Akademiya Na Naukite: 713-716

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