The Effect of Amino Acid Mixtures, Insulin, Epinephrine and Glucagon in vivo on the Levels of Rat Liver Tyrosine Aminotransferase

1969 ◽  
Vol 10 (2) ◽  
pp. 113-121 ◽  
Author(s):  
L. Reshef ◽  
O. Greengard
Keyword(s):  
Amino Acid ◽  
Rat Liver ◽  
Tyrosine Aminotransferase ◽  
Amino Acid Mixtures

scholarly journals Inactivation of tyrosine aminotransferase in neutral homogenates and rat liver slices

1972 ◽  
Vol 129 (5) ◽  
pp. 1131-1138 ◽  
Author(s):  
F. Auricchio ◽  
L. Mollica ◽  
A. Liguori
Keyword(s):  
Amino Acid ◽  
Rat Liver ◽  
Acid Concentration ◽  
Tyrosine Aminotransferase ◽  
Amino Acid Concentration ◽  
Acidic Ph ◽  
Ph Values ◽  
Neutral Ph ◽  
Liver Slices

Inactivation of tyrosine aminotransferase induced in vivo by triamcinolone was studied in a homogenate incubated at neutral pH values. The integrity and the presence of subcellular particles together with a compartment of acidic pH are necessary for inactivation of tyrosine aminotransferase. It is suggested that tyrosine aminotransferase is inactivated inside lysosomes. The system responsible for inactivation of tyrosine aminotransferase was partially purified and identified with lysosomal cathepsins B and B1. Inactivation of tyrosine aminotransferase in liver slices is controlled by the amino acid concentration and strongly stimulated by cysteine. 3,3′,5-Tri-iodo-l-thyronine reversibly and strongly decreases the rate of inactivation of tyrosine aminotransferase. The effect is not due to an increased rate of tyrosine aminotransferase synthesis.

scholarly journals The effects of salicylate on the activity of rat liver tyrosine–2-oxoglutarate aminotransferase in vitro and in vivo

1972 ◽  
Vol 126 (2) ◽  
pp. 347-350 ◽  
Author(s):  
A. A.-B. Badawy
Keyword(s):  
Rat Liver ◽  
Pyridoxal Phosphate ◽  
Actinomycin D ◽  
Sodium Salicylate ◽  
Intraperitoneal Administration ◽  
Tyrosine Aminotransferase ◽  
Major Effect ◽  
Endogenous Activity

1. Salicylate, in concentrations of 0.25mm and above, enhances the basal activity of tyrosine–2-oxoglutarate aminotransferase in homogenates of rat liver incubated in the absence of added pyridoxal 5′-phosphate (endogenous activity). The effect is decreased by increasing the concentration of the cofactor. 2. The intraperitoneal administration of sodium salicylate enhances the activity of rat liver tyrosine aminotransferase; the major effect during the first hour being on the enzyme in the absence of added pyridoxal phosphate. Actinomycin D prevents the induction of the enzyme by cortisol and tryptophan. Induction by pyridoxine or salicylate is 50% inhibited by actinomycin D. The effects of the injections of various combinations of cortisol, pyridoxine and salicylate were also studied in the absence or presence of actinomycin D. 3. It is suggested that salicylate induces rat liver tyrosine aminotransferase by displacing its protein-bound cofactor and that a cofactor-type induction of the hepatic enzyme occurs in pyridoxine-treated rats.

scholarly journals Biotin-mediated protein biosynthesis

1974 ◽  
Vol 140 (3) ◽  
pp. 549-556 ◽  
Author(s):  
R. L. Boeckx ◽  
K. Dakshinamurti
Keyword(s):  
Protein Synthesis ◽  
Amino Acid ◽  
Rat Liver ◽  
Intestinal Mucosa ◽  
Protein Biosynthesis ◽  
Amino Acid Incorporation ◽  
Acid Incorporation ◽  
Stimulation Of

The effect of administration of biotin to biotin-deficient rats on protein biosynthesis was studied. Biotin treatment resulted in stimulation by more than twofold of amino acid incorporation into protein, both in vivo and in vitro in rat liver, pancreas, intestinal mucosa and skin. Analysis of the products of amino acid incorporation into liver proteins in vivo and in vitro indicated that the synthesis of some proteins was stimulated more than twofold, but others were not stimulated at all. This indicates a specificity in the stimulation of protein synthesis mediated by biotin.

l-Tryptophan inhibition of tyrosine aminotransferase degradation in rat liver in vivo

1973 ◽  
Vol 156 (1) ◽  
pp. 188-194 ◽  
Author(s):  
Alois Cihak ◽  
Carlos Lamar ◽  
Henry C. Pitot
Keyword(s):  
Rat Liver ◽  
Tyrosine Aminotransferase

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.

scholarly journals The effect of feeding with a tryptophan-free amino acid mixture on rat liver magnesium ion-activated deoxyribonucleic acid-dependent ribonucleic acid polymerase

1970 ◽  
Vol 120 (1) ◽  
pp. 205-214 ◽  
Author(s):  
A. R. Henderson
Keyword(s):  
Amino Acid ◽  
Rna Polymerase ◽  
Rat Liver ◽  
Acid Concentration ◽  
Polymerase Activity ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Amino Acid Mixtures ◽  
Rna Polymerase Activity ◽  
Tryptophan Concentration

1. The Widnell & Tata (1966) assay method for Mg2+-activated DNA-dependent RNA polymerase was used for initial-velocity determinations of rat liver nuclear RNA polymerase. One unit (U) of RNA polymerase was defined as that amount of enzyme required for 1 mmol of [3H]GMP incorporation/min at 37°C. 2. Colony fed rats were found to have a mean RNA polymerase activity of 65.9μU/mg of DNA and 18h-starved rats had a mean activity of 53.2μU/mg of DNA. Longer periods of starvation did not significantly decrease RNA polymerase activity further. 3. Rats that had been starved for 18h were used for all feeding experiments. Complete and tryptophan-deficient amino acid mixtures were given by stomach tube and the animals were killed 15–120min later. The response of RNA polymerase to the feeding with the complete amino acid mixture was rapid and almost linear over the first hour of feeding, resulting in a doubling of activity. The activity was still elevated above the starvation value at 120min after feeding. The tryptophan-deficient amino acid mixture produced a much less vigorous response about 45min after the feeding, and the activity had returned to the starvation value by 120min after the feeding. 4. The response of RNA polymerase to the feeding with the complete amino acid mixture was shown to occur within a period of less than 5min to about 10min after the feeding. 5. Pretreatment of the animals with puromycin or cycloheximide was found to abolish the 15min RNA polymerase response to the feeding with the complete amino acid mixture, but the activity of the controls was unaffected. 6. The characteristics of the RNA polymerase from 18h-starved animals and animals fed with the complete or incomplete amino acid mixtures for 1h were examined. The effects of Mg2+ ions, pH, actinomycin D and nucleoside triphosphate omissions were determined. The [Mg2+]– and pH–activity profiles of the RNA polymerase from the animal fed with the complete mixture appeared to differ from those of the enzyme from the other groups, but this difference is probably not significant. 7. [5-3H]Orotic acid incorporation by rat liver nuclei in vivo was shown to be affected by the amino acid mixtures in a similar manner to the RNA polymerase. 8. The tryptophan concentrations of plasma and liver were determined up to 120 min after feeding with the amino acid mixtures. Feeding with the complete mixture produced a rapid increase in free tryptophan concentrations in both plasma and liver, but feeding with the incomplete mixture did not alter the plasma concentration. The liver tryptophan concentration increased at about 45min after feeding with the tryptophan-deficient diet. 9. There was a good correlation between the liver tryptophan concentration and RNA polymerase activity in all groups of animals. 10. It was concluded that the rat liver nucleus responded to an increase in amino acid supply by increased synthesis of RNA as a result of synthesis of RNA polymerase de novo. The correlation of tryptophan concentration and RNA polymerase activity appears to reflect the general amino acid concentration required to support hepatic protein synthesis and to produce new RNA polymerase. This new polymerase appears to differ from the basal RNA polymerase by its rapid synthesis and destruction, which may be a means of regulating RNA synthesis by the amino acid concentration in the liver.

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