scholarly journals The effects of salicylate on the activity of rat liver tryptophan pyrrolase in vitro and in vivo

1971 ◽  
Vol 123 (2) ◽  
pp. 171-174 ◽  
Author(s):  
A. A.-B. Badawy ◽  
M. J. H. Smith
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Binding Sites ◽  
Actinomycin D ◽  
Sodium Salicylate ◽  
Progressive Increase ◽  
Tryptophan Pyrrolase ◽  
Enzyme Ratio

1. Salicylate, in concentrations of 0.05mm and above, inhibits the basal activity of tryptophan pyrrolase in homogenates of rat liver and the activity induced by cortisol but not that induced by tryptophan. The inhibition is abolished by adding haematin to the reaction mixtures. 2. The intraperitoneal injection of 400mg of sodium salicylate/kg in the rat causes a decrease in the tryptophan pyrrolase activity in the liver at 30min, the activity is restored to normal at 2h, increases to sixfold after 5h and returns to the basal value at 12h. The activation of the enzyme by salicylate is prevented by the administration of cycloheximide but not by pretreatment with actinomycin D. The effects of the combined injection of salicylate and cortisol are additive, whereas those of salicylate plus tryptophan are not. The injection of salicylate causes a progressive increase in the holo-/apo-enzyme ratio and an increased content of tryptophan in the liver over a period of 3h. 3. It is suggested that salicylate inhibits tryptophan pyrrolase activity in vitro and in vivo by interacting with iron protoporphyrins and causes a later enhancement of the enzyme activity in vivo by a mechanism involving the release of tryptophan from its binding sites on circulating albumin and on other proteins.

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 ANTIGENIC MODULATION

1968 ◽  
Vol 127 (3) ◽  
pp. 523-539 ◽  
Author(s):  
Lloyd J. Old ◽  
Elisabeth Stockert ◽  
Edward A. Boyse ◽  
Jae Ho Kim
Keyword(s):  
Actinomycin D ◽  
Progressive Increase ◽  
The Other ◽  
Antigenic Modulation ◽  
Cytotoxic Test ◽  
Cell Divisions ◽  
Wide Range ◽  
D Region

Antigenic modulation (the loss of TL antigens from TL+ cells exposed to TL antibody in the absence of lytic complement) has been demonstrated in vitro. An ascites leukemia, phenotype TL.1,2,3, which modulates rapidly and completely when incubated with TL antiserum in vitro, was selected for further study of the phenomenon. Over a wide range of TL antibody concentrations modulation at 37°C was detectable within 10 min and was complete within approximately 1 hr. The cells were initially sensitized to C' by their contact with antibody, thereafter losing this sensitivity to C' lysis together with their sensitivity to TL antibody and C' in the cytotoxic test. The capacity of the cells to undergo modulation was abolished by actinomycin D and by iodoacetamide, and by reducing the temperature of incubation to 0°C. Thus modulation apparently is an active cellular process. Antigens TL. 1,2, and 3 are all modulated by anti-TL.1,3 serum and by anti-TL.3 serum. This modulation affects all three TL components together, even when antibody to one or two of them is lacking. aAnti-TL.2 serum does not induce modulation and in fact impairs modulation by the other TL antibodies. The influence of the TL phenotype of cells upon the demonstrable content of H-2 (D region) isoantigen, first shown in cells modulated in vivo, has been observed with cells modulated in vitro. Cells undergoing modulation show a progressive increase in H-2 (D region) antigen over a period of 4 hr, with no change in H-2 antigens of the K region. Restoration of the TL+ phenotype of modulated cells after removal of antibody is less rapid than TL+ → TL- modulation and may require several cell divisions.

The relationship between Mg2+-stimulated ATPase activity and glycogen content in rat liver

1969 ◽  
Vol 47 (3) ◽  
pp. 339-345 ◽  
Author(s):  
B. Rubenstein ◽  
P. G. Scholefield
Keyword(s):  
Enzyme Activity ◽  
Atpase Activity ◽  
Rat Liver ◽  
Glycogen Content ◽  
Phosphorylase Activity ◽  
Tumor Bearing ◽  
Physical Association ◽  
The Relationship

During starvation there is an increase in the ATPase activity of a postmitochondrial fraction of rat liver. The increase is relatively specific for ATP and there is no change in the Na+,K+-stimulated ATPase activity. A corresponding increase in ATPase activity is found on pretreatment of the rat with glucagon and in tumor-bearing animals. The increase has been correlated with increase in phosphorylase activity and decrease in glycogen content under in vivo and in vitro conditions. Treatment of fasted animals with glucose or sucrose restores the glycogen content and diminishes the ATPase activity to normal levels, but puromycin is without effect. It is proposed that a physical association of glycogen with Mg2+-stimulated ATPase activity prevents the enzyme activity from being expressed.

scholarly journals Studies of the Stability in Vivo and in Vitro of Rat Liver Tryptophan Pyrrolase

1965 ◽  
Vol 240 (12) ◽  
pp. 4609-4620 ◽  
Author(s):  
Robert T. Schimke ◽  
E.W. Sweeney ◽  
C.M. Berlin
Keyword(s):  
Rat Liver ◽  
Tryptophan Pyrrolase ◽  
The Stability

scholarly journals Studies of the ethylation of rat liver transfer ribonucleic acid after administration of l-ethionine

1972 ◽  
Vol 128 (1) ◽  
pp. 59-68 ◽  
Author(s):  
A. E. Pegg
Keyword(s):  
Rat Liver ◽  
Ribonucleic Acid ◽  
Major Part ◽  
Actinomycin D ◽  
Major Product ◽  
The Other ◽  
Methyl Donor ◽  
Principal Product

1. The ethylated nucleosides present in tRNA isolated from the livers of rats treated with 0.5g of l-ethionine/kg body wt. were investigated. Evidence that this tRNA contained N2-ethylguanine, N2N2-diethylguanine, N2-ethyl-N2-methylguanine, 7-ethylguanine, two ethylated pyrimidines and ethylated ribose groups was obtained. 2. Ethylation of bacterial tRNA was catalysed by extracts containing tRNA methylases prepared from rat liver by using S-adenosyl-l-ethionine as an ethyl donor, but the rate of ethylation was 20 times less than the rate of methylation with S-adenosyl-l-methionine as a methyl donor. 3. The principal product of such ethylation in vitro was N2-ethylguanine and traces of the other ethylated guanines and pyrimidines found in tRNA isolated from rats treated with ethionine in vivo were also found. 1-Ethyladenine was not formed, although 1-methyl-adenine is a major product of methylation of bacterial tRNA by these extracts, and 1-ethyladenine was not present in the rat liver tRNA isolated from ethionine-treated animals. 4. After injection of actinomycin D (15mg/kg body wt.) or l-methionine (1.0g/kg body wt.) before the ethionine, ethylation of tRNA was diminished by about 80% but not completely abolished. Administration of 1-aminocyclopentanecarboxylic acid (2.5g/kg body wt.) to inhibit the formation of S-adenosyl-l-ethionine inhibited ethylation of tRNA by 44%. 5. These results suggest that not all of the ethylation of tRNA that occurs in the livers of rats treated with ethionine is mediated by the action of tRNA methylases acting with S-adenosyl-l-ethionine as a substrate, but that this pathway does occur and accounts for a major part of the observed ethylation. 6. The results are discussed with reference to ethionine-induced hepatocarcinogenesis.

scholarly journals Characterization of binding sites for acetylated low density lipoprotein in the rat liver in vivo and in vitro.

1985 ◽  
Vol 4 (5) ◽  
pp. 1157-1162 ◽  
Author(s):  
H.A. Dresel ◽  
E. Friedrich ◽  
D.P. Via ◽  
G. Schettler ◽  
H. Sinn
Keyword(s):  
Rat Liver ◽  
Binding Sites ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Low Density

scholarly journals The effects of acute and chronic nicotine hydrogen (+)-tartrate administration and subsequent withdrawal on rat liver tryptophan pyrrolase activity and their comparison with those of morphine, phenobarbitone and ethanol

1975 ◽  
Vol 148 (3) ◽  
pp. 425-432 ◽  
Author(s):  
A A Badawy ◽  
M Evans
Keyword(s):  
Rat Liver ◽  
Acute Administration ◽  
Nicotine Treatment ◽  
Chronic Nicotine ◽  
Nicotine Administration ◽  
Hormonal Mechanism ◽  
Tryptophan Pyrrolase ◽  
Subsequent Withdrawal

Acute administration of nicotine hydrogen (+)-tartrate enhances the activity of rat liver tryptophan pyrrolase by a hormonal mechanism. Chronic nicotine treatment inhibits, and subsequent withdrawal enhances, the pyrrolase activity. The inhibition during chronic treatment is not due to a defective apoenzyme synthesis nor a decreased cofactor availability. Regeneration of liver NADP+ in vitro and in vivo reverses the inhibition. Chronic nicotine administration increases the liver NADPH concentration. The above effects of nicotine resemble to a remarkable degree those previously shown for morphine, phenobarbitone and ethanol. All effects are compared, and their possible significance in relation to drug dependence is discussed.

Effect of yohimbine on 14CO2 production from 14C-pyrrole-ring-labeIed DL-tryptophan in rats treated with L-tryptophan, DL-α-methyltryptophan, and Cortisol

1969 ◽  
Vol 47 (11) ◽  
pp. 1049-1052 ◽  
Author(s):  
Theodore L. Sourkes ◽  
Krystyna Missala
Keyword(s):  
Pyrrole Ring ◽  
Active Form ◽  
Inhibitory Effect ◽  
Progressive Increase ◽  
Prior Treatment ◽  
Tryptophan Oxidation ◽  
14Co2 Production ◽  
Tryptophan Pyrrolase

Yohimbine, previously shown to inhibit tryptophan pyrrolase in vitro and in vivo, was tested in rats whose pyrrolase activity had been elevated by prior treatment with cortisol, tryptophan, or α-methyltryptophan. The alkaloid exerted an inhibitory effect on the oxidation of tryptophan-2-(pyrrole ring)-14C in rats given Cortisol or α-methyltryptophan, but had no effect on those given tryptophan loads. Consideration of the respective modes of action of the three stimulators of tryptophan pyrrolase activity and the observed results suggests that yohimbine acts at the stage of reduction of holoenzyme to its active form, a process requiring L-tryptophan.The oxidation of 14C-tryptophan in vivo seems to involve a progressive increase in the activity of pyrrolase during the first 1–1.5 h. By prior treatment of rats with tryptophan loads, the oxidation approaches a linear, but submaximal, rate during this period. The size of the air-pool in the metabolic cages (dead space) does not introduce, within the limits studied, an artifact into the measurements of the rate of tryptophan oxidation in vivo.

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