Biomaterial Database

Hormonal deinduction of tyrosine aminotransferase. 1982

E M Giesen, and G Beck

The effects of several antagonists of glucocorticoid action on a line of hepatoma cells (HTC strain) have been studied in order to determine their mechanisms of action. The induction of tyrosine aminotransferase by dexamethasone can be partially or totally inhibited if an antagonist is added simultaneously with dexamethasone or some time later. Antagonists, even if they have as much affinity for the cytoplasmic receptor as dexamethasone, must be administered at a 100-fold excess as compared to dexamethasone. Their receptor binding kinetics are not identical to those of inducer steroids: moreover there is no correlation between relative binding affinities and anti-inducing capacities. A short contact between the cells and the antagonist is sufficient to obtain a full antagonistic effect, but the antagonist is inactive if administered and removed from the cells before induction. An interpretation if suggested, considering these results which do not find a satisfactory explanation in the classical theory of receptor action.

UI	MeSH Term	Description	Entries
D008114	Liver Neoplasms, Experimental	Experimentally induced tumors of the LIVER.	Hepatoma, Experimental,Hepatoma, Morris,Hepatoma, Novikoff,Experimental Hepatoma,Experimental Hepatomas,Experimental Liver Neoplasms,Hepatomas, Experimental,Neoplasms, Experimental Liver,Experimental Liver Neoplasm,Liver Neoplasm, Experimental,Morris Hepatoma,Novikoff Hepatoma
D003907	Dexamethasone	An anti-inflammatory 9-fluoro-glucocorticoid.	Hexadecadrol,Decaject,Decaject-L.A.,Decameth,Decaspray,Dexasone,Dexpak,Hexadrol,Maxidex,Methylfluorprednisolone,Millicorten,Oradexon,Decaject L.A.
D004790	Enzyme Induction	An increase in the rate of synthesis of an enzyme due to the presence of an inducer which acts to derepress the gene responsible for enzyme synthesis.	Induction, Enzyme
D005938	Glucocorticoids	A group of CORTICOSTEROIDS that affect carbohydrate metabolism (GLUCONEOGENESIS, liver glycogen deposition, elevation of BLOOD SUGAR), inhibit ADRENOCORTICOTROPIC HORMONE secretion, and possess pronounced anti-inflammatory activity. They also play a role in fat and protein metabolism, maintenance of arterial blood pressure, alteration of the connective tissue response to injury, reduction in the number of circulating lymphocytes, and functioning of the central nervous system.	Glucocorticoid,Glucocorticoid Effect,Glucorticoid Effects,Effect, Glucocorticoid,Effects, Glucorticoid
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014444	Tyrosine Transaminase	An enzyme that catalyzes the conversion of L-TYROSINE and 2-oxoglutarate to 4-hydroxyphenylpyruvate and L-GLUTAMATE. It is a pyridoxal-phosphate protein. L-PHENYLALANINE is hydroxylated to L-tyrosine. The mitochondrial enzyme may be identical with ASPARTATE AMINOTRANSFERASES (EC 2.6.1.1.). Deficiency of this enzyme may cause type II Tyrosinemia (see TYROSINEMIAS). EC 2.6.1.5.	Tyrosine Aminotransferase,Aminotransferase, Tyrosine,Transaminase, Tyrosine