scholarly journals Tryptophan aminotransferase activity in rat liver

1984 ◽  
Vol 220 (1) ◽  
pp. 341-344 ◽  
Author(s):  
J C Stanley ◽  
A R Nicholas ◽  
A J Dickson ◽  
I M Thompson ◽  
C I Pogson
Keyword(s):  
Rat Liver ◽  
Enzyme Induction ◽  
Tyrosine Aminotransferase ◽  
The Other ◽  
Aminotransferase Activity

By using an antiserum raised against rat liver tyrosine aminotransferase, it was shown that about 60% of tryptophan aminotransferase activity in rat liver extracts is catalysed by this enzyme. Induction of tryptophan aminotransferase activity by intraperitoneal injections of tryptophan or triamcinolone can be entirely attributed to the effects of these agents on tyrosine aminotransferase. The origin of the other 40% of tryptophan aminotransferase activity remains to be established. This activity increases after starvation for 48 h. It is unlikely that tryptophan transamination plays a quantitatively important role in the metabolism of tryptophan by the liver.

scholarly journals Biphasic effect of acute ethanol administration on rat liver tyrosine-2-oxoglutarate aminotransferase activity

1980 ◽  
Vol 186 (3) ◽  
pp. 755-761 ◽  
Author(s):  
A A B Badawy ◽  
B M Snape ◽  
M Evans
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Actinomycin D ◽  
Tyrosine Aminotransferase ◽  
Ethanol Metabolism ◽  
Ethanol Administration ◽  
Aminotransferase Activity ◽  
Biphasic Effect ◽  
Initial Decrease ◽  
Acute Ethanol

1. Acute ethanol administration causes a biphasic change in rat liver tyrosine aminotransferase activity. 2. The initial decrease is significant with a 200 mg/kg dose of ethanol, is prevented by adrenoceptor-blocking agnets and by reserpine, but not by inhibitors of ethanol metabolism, and exhibits many of the characteristics of the inhibition caused by noradrenaline. 3. The subsequent enhancement of the enzyme activity by ethanol is not associated with stabilization of the enzyme, but is sensitive to actinomycin D and cycloheximide. 4. It is suggested that the initial decrease in aminotransferase activity is caused by the release of catecholamines, whereas the subsequent enhancement may be related to the release of glucocorticoids.

Enzyme induction in rat liver: The effects of Be2+in vivo

1981 ◽  
Vol 1 (3) ◽  
pp. 217-222 ◽  
Author(s):  
Margery G. Ord ◽  
Lloyd A. Stocken
Keyword(s):  
Protein Kinase ◽  
Rat Liver ◽  
Enzyme Induction ◽  
Orotic Acid ◽  
Tyrosine Aminotransferase ◽  
Cytoplasmic Protein ◽  
Ribonucleoprotein Particles ◽  
Liver Nuclei

Rats given an LD50 dose of Be2+ showed reduced activities of ornithine decarboxytase and tyrosine aminotransferase in liver in response to dexamethasone induction. Control fed animals showed ‘superinduction’. Be2+ also inhibited the uptake of [3H]orotic acid into rapidly labelled RNA of ribonucleoprotein particles extracted from liver nuclei in isomolar solutions at pH 8.0. Consistent with inhibition of cytoplasmic protein kinase reported previously (Kaser et at., 1980), the uptake of [32P]Pi into proteins in the ribonucleoprotein particles was also diminished.

Diurnal variations in inducibility of rat liver tyrosine aminotransferase activity

Life Sciences ◽  
1978 ◽  
Vol 23 (12) ◽  
pp. 1301-1308 ◽  
Author(s):  
James A. Gurr ◽  
Robert S. Elvehjem ◽  
Van R. Potter
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Diurnal Variations ◽  
Aminotransferase Activity

O n the Mechanism of Inactivation and ATP-Dependent Reactivation of Rat Liver Tyrosine Aminotransferase

1977 ◽  
Vol 32 (9-10) ◽  
pp. 777-780 ◽  
Author(s):  
Hans-Heinrich Hamm ◽  
Werner Seubert
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Particulate Fraction ◽  
Kidney Cortex ◽  
Aminotransferase Activity ◽  
Liver And Kidney ◽  
Membrane Bound ◽  
Nucleotide Specificity

Abstract The mechanism of in vitro inactivation and ATP-dependent rapid reactivation of rat liver tyrosine aminotransferase by a membrane-bound system from rat liver and kidney cortex and the nucleotide specificity of this process was investigated using partially purified tyrosine amino­ transferase as a substrate. Adenosine 5′-triphosphate (ATP) could be replaced by guanosine 5′-tri-phosphate (GTP), whereas inosine 5′-triphosphate (ITP) was less effective. During reactivation [γ-32P]A T P was incorporated into the enzyme and not excorporated by incubation of the labeled enzyme with excess non-radioative ATP. Inactivation of labeled tyrosine aminotransferase by a particulate fraction led to a decrease protein-bound radioactivity concomitant with an increase of [32P] orthophosphate. This points to a phosphorylation and dephosphorylation mechanism in the regulation of tyrosine aminotransferase activity.

scholarly journals The effect of cytosine arabinoside and bromodeoxyuridine on the appearance of tyrosine aminotransferase in cultured foetal hepatocytes of the rat

1980 ◽  
Vol 188 (3) ◽  
pp. 929-932 ◽  
Author(s):  
G C Yeoh ◽  
I T Oliver
Keyword(s):  
Cell Differentiation ◽  
Rat Liver ◽  
Cytosine Arabinoside ◽  
Culture Medium ◽  
Tyrosine Aminotransferase ◽  
Aminotransferase Activity ◽  
Inhibitory Effects ◽  
Foetal Liver ◽  
Foetal Rat

1. The acquisition of dexamethasone-inducibility of tyrosine aminotransferase activity by hepatocytes cultured from 15-day-foetal rat liver is blocked in the presence of cytosine arabinoside. 2. Similar results are obtained in the presence of bormodeoxyuridine. 3. No effects on steroid-inducibility of tyrosine aminotransferase are obtained with either of the above compounds in hepatocytes cultured from 19-day-foetal liver. 4. the inhibitory effects of the agents are substantially reversed after their removal from the culture medium. 5. The effects of bromodeoxyuridine suggest that cell differentiation, with respect to tyrosine aminotransferase-inducibility, occurs in cultures of 15-day-doetal hepatocytes. 6. The effects of cytosine arabinoside suggest that such an event is dependent on mitosis.

scholarly journals Stabilization of rat liver tyrosine aminotransferase by tetracycline

1975 ◽  
Vol 150 (3) ◽  
pp. 329-333 ◽  
Author(s):  
R Hannah ◽  
M K Sahib
Keyword(s):  
Rat Liver ◽  
De Novo ◽  
Rabbit Antiserum ◽  
Tyrosine Aminotransferase ◽  
Enzyme Inactivation ◽  
Aminotransferase Activity ◽  
Rapid Inactivation ◽  
Liver Homogenates

Rat liver tyrosine aminotransferase was purified 200-fold and an antiserum raised against it in rabbits. 2. Hepatic tyrosine aminotransferase activity was increased fourfold by tyrosine, twofold by tetracycline, 2.5-fold by cortisone 21-acetate and ninefold by a combination of tyrosine and cortisol administered intraperitoneally to rats. 3. Radioimmunoassay with 14C-labelled tyrosine aminotransferase, in conjunction with rabbit antiserum against the enzyme, revealed that cortisol stimulates the synthesis of the enzyme de novo, but that tetracycline has no such effect. 4. Incubation of rat liver homogenates with purified tyrosine aminotransferase in vitro leads to a rapid inactivation of the enzyme, which tetracycline partially inhibits. 5. The inactivation is brought about by intact lysosomes, and the addition of 10mM-cysteine increases the rate of enzyme inactivation, which is further markedly increased by 10mM-Mg2+ and 10mM-ATP. Here again tetracycline partially inhibits the decay rate, leading to the inference that the increase of tyrosine aminotransferase activity in vivo by tetracycline is brought about by the latter inhibiting the lysosomal catheptic action.

scholarly journals Rat liver tyrosine aminotransferase activity and induction by dexamethasone upon cadmium intoxication

2003 ◽  
Vol 55 (1-2) ◽  
pp. 3-7 ◽  
Author(s):  
Jadranka Dundjerski ◽  
Jelena Predic ◽  
Aleksandra Cvoro ◽  
Gordana Matic
Keyword(s):  
Enzyme Activity ◽  
Gene Transcription ◽  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Aminotransferase Activity ◽  
Liver Cytosol ◽  
Cadmium Intoxication ◽  
Rat Liver Cytosol

This study was focused on Cd effects on basal and dexamethasone-induced tyrosine aminotransferase (TAT) activity in the rat liver cytosol. Cadmium (Cd), applied in the dose of 2 mg/kg b.w., stimulated both TAT activity and its induction by dexamethasone, inducing the most prominent alterations 24 h after administration. Doses lower than 2 mg Cd/kg b.w. were ineffective while the higher ones (3 and 4 mg Cd/kg b.w) led to the changes similar to those reached by 2 mg Cd/kg. The in vitro application of different Cd concentrations to the liver cytosol rendered the enzyme activity unchanged suggesting that the metal acted at the level of TAT gene transcription.

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