scholarly journals Effect of environmental stress of low pressure on tyrosine aminotransferase and phenylalanine 4-hydroxylase activities in the rat

1975 ◽  
Vol 150 (2) ◽  
pp. 263-268 ◽  
Author(s):  
M A A Namboodiri ◽  
T Ramasarma
Keyword(s):  
Environmental Stress ◽  
Actinomycin D ◽  
Phenylalanine Hydroxylase ◽  
Low Pressure ◽  
Tyrosine Aminotransferase ◽  
Aminotransferase Activity ◽  
Hydroxylase Activity ◽  
Environmental Pressure ◽  
Pressure Decrease

1. Tyrosine aminotransferase activity in the liver increased about fourfold after 9h, on exposure of rats to stress of low pressure. 2. The phenylalanine hydroxylase activity increased about 60% on exposure for 24h or more. 3. An environmental pressure decrease of about 0.033 MN/m2 is needed to increase the activity of tyrosine aminotransferase. 4. Adrenalectomy completely abolished the increase in activity of tyrosine aminotransferase obtained on exposure to low pressure. 5. Treatment with cycloheximide or actinomycin D prevented the increase in activity of tyrosine aminotransferase. 6. Treatment with cycloheximide at the early part of exposure to stress prevented the increase in activity of phenylalanine hydroxylase obtained after 24h.

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.

scholarly journals Tyrosine aminotransferase induction in hepatocytes cultured from rat foetuses treated with dexamethasone in utero

1979 ◽  
Vol 180 (3) ◽  
pp. 545-549 ◽  
Author(s):  
G C T Yeoh ◽  
T Arbuckle ◽  
I T Oliver
Keyword(s):  
Culture Medium ◽  
Actinomycin D ◽  
Tyrosine Aminotransferase ◽  
In Utero ◽  
Aminotransferase Activity ◽  
Foetal Liver ◽  
Translational Block ◽  
Cells Cultured ◽  
Specific Mrna

1. The administration of dexamethasone to foetal rats in utero does not result in the appearance of specific tyrosine aminotransferase activity even after 24 h. 2. When foetal hepatocytes are cultured in vitro from animals treated in utero with dexamethasone, significantly higher activities of specific tyrosine aminotransferase are found than in untreated controls. 3. Dexamethasone in vitro induces specific tyrosine aminotransferase in cells cultured from control animals and the effect is maximal at 10 nM in the culture medium. 4. Actinomycin D at 0.2 microgram/ml in the culture medium completely prevents the induction of activity in vitro. 5. In cultures established from animals treated with dexamethasone in utero, the increase in specific tyrosine aminotransferase activity over the control cultures is only marginally decreased in the presence of actinomycin D. 6. The results can be interpreted to mean that dexamethasone in utero stimulates the transcription of enzyme-specific mRNA, which is not rranslated until a translational block in the foetal liver is removed by the conditions of culture in vitro.

scholarly journals Effect of hypobaric stress on enzymes of tryptophan metabolism

1972 ◽  
Vol 127 (3) ◽  
pp. 509-514 ◽  
Author(s):  
A. R. Inamdar ◽  
C. K. Ramakrishna Kurup ◽  
T. Ramasarma
Keyword(s):  
Enzyme Activities ◽  
Tryptophan Hydroxylase ◽  
Prolonged Exposure ◽  
Repeated Administration ◽  
Tyrosine Aminotransferase ◽  
Aminotransferase Activity ◽  
Hydroxylase Activity ◽  
Tryptophan Pyrrolase ◽  
Tryptophan Hydroxylase Activity ◽  
Prior Administration

1. On exposure of rats to hypobaric stress the tryptophan pyrrolase and tyrosine aminotransferase activities of the liver increased about threefold in 4h. 2. The tryptophan hydroxylase activity increased about 50% on exposure for 24h or more. 3. The increased activities reverted to the basal value on removal of the stress. 4. Treatment with cycloheximide inhibited the increase in the enzyme activities when the time of exposure was short (4h). However, the inhibitor-treated animals showed paradoxically high tyrosine aminotransferase activity on prolonged exposure (24h). 5. The pattern of haematin saturation indicated that the increase in pyrrolase activity under low pressure resembled that obtained with cortisol and not with tryptophan. 6. Repeated administration of cortisol or tryptophan did not have any effect on the activity of tryptophan hydroxylase. 7. The stress-induced increase in hydroxylase activity was not eliminated by the prior administration of 5-hydroxytryptophan to the animals.

scholarly journals Effect of glucagon on phenylalanine metabolism and phenylalanine-degrading enzymes in the rat

1974 ◽  
Vol 142 (2) ◽  
pp. 231-245 ◽  
Author(s):  
Larry M. Brand ◽  
Alfred E. Harper
Keyword(s):  
Urinary Excretion ◽  
Oxidation Rate ◽  
Phenylalanine Hydroxylase ◽  
Dihydropteridine Reductase ◽  
Aminotransferase Activity ◽  
Hydroxylase Activity ◽  
Phenylalanine Metabolism ◽  
Rate Limiting ◽  
Reduced State

Glucagon administered subcutaneously to rats for 10 days had no significant effect on liver phenylalanine hydroxylase activity, but induced liver dihydropteridine reductase more than twofold. In rats administered a phenylalanine load orally, glucagon treatment stimulated oxidation and depressed urinary phenylalanine excretion. These responses could not be related to an effect of glucagon on hepatic tyrosine–α-oxoglutarate aminotransferase activity. Even in rats with phenylalanine hydroxylase activity depressed to 50% of control values by p-chlorophenylalanine administration, glucagon treatment increased the phenylalanine-oxidation rate substantially. Although hepatic phenylalanine–pyruvate aminotransferase was increased tenfold in glucagon-treated rats, glucagon treatment did not increase urinary excretion of phenylalanine transamination products by rats given a phenylalanine load. Glucagon treatment did not affect phenylalanine uptake by the gut or liver, or the liver content of phenylalanine hydroxylase cofactor. It is suggested that dihydropteridine reductase is the rate-limiting enzyme in phenylalanine degradation in the rat, and that glucagon may regulate the rate of oxidative phenylalanine metabolism in vivo by promoting indirectly the maintenance of the phenylalanine hydroxylase cofactor in its active, reduced state.

scholarly journals Role of adrenaline and cyclic AMP in appearance of tyrosine aminotransferase in perinatal rat liver

1980 ◽  
Vol 190 (3) ◽  
pp. 685-690 ◽  
Author(s):  
A V Ghisalberti ◽  
J G Steele ◽  
M H Cake ◽  
M C McGrath ◽  
I T Oliver
Keyword(s):  
Cyclic Amp ◽  
Culture Medium ◽  
Actinomycin D ◽  
Cultured Cells ◽  
Tyrosine Aminotransferase ◽  
Newborn Rats ◽  
Aminotransferase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Old Rats

1. Adrenaline increased hepatic tyrosine aminotransferase activity when injected into foetal rats or 2-day-old rats. 2. The inhibition of the postnatal increase in tyrosine aminotransferase activity which occurred in adrenalectomized newborn rats rapidly overcome by injection of adrenaline or dibutyryl cyclic AMP. 3. The effects of adrenaline or dibutyryl cyclic AMP on the tyrosine aminotransferase activity in foetal, adrenalectomized newborn and 2-day-old rats could be partially or completely blocked by prior treatment with actinomycin D. 4. Dibutyryl cyclic AMP induced tyrosine aminotransferase activity in hepatocytes cultured from 15-day foetal rats in glucocorticoid-free medium. 5. Actinomycin D at 0.2 microgram/ml in the culture medium completely prevented the induction of tyrosine aminotransferase activity by dibutyryl cyclic AMP in cultured cells. 6. The results suggest that adrenaline and cyclic AMP stimulate a transcriptional event during induction of tyrosine aminotransferase in perinatal liver.

scholarly journals Factors affecting the premature induction of tyrosine aminotransferase in foetal rat liver

1968 ◽  
Vol 108 (2) ◽  
pp. 333-338 ◽  
Author(s):  
P. G. Holt ◽  
I. T. Oliver
Keyword(s):  
Actinomycin D ◽  
Tyrosine Aminotransferase ◽  
Premature Delivery ◽  
Aminotransferase Activity ◽  
Foetal Development ◽  
Factors Affecting ◽  
Foetal Liver ◽  
Amino Acid Analogues ◽  
Lag Period

1. Premature delivery of foetal rats by uterine section results in the rapid appearance of tyrosine aminotransferase activity in foetal liver, after an initial lag period of 3–6hr. 2. The premature induction of activity is completely repressible by actinomycin D given soon after delivery and partially repressible by puromycin and amino acid analogues. 3. Glucagon injections into foetal rats in utero lead to production of tyrosine aminotransferase in the foetal liver, but adrenalin and nor-adrenalin are without effect. 4. Injections of glucose, galactose, fructose and mannose into prematurely delivered rats repress the development of tyrosine aminotransferase activity about 50% when they are given 2hr. after delivery, but glucose has no significant effect when injected at delivery. 5. The results are discussed in relation to current hypotheses on the role of hormones in enzyme induction in foetal development.

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.

Development of phenylalanine hydroxylase activity in guinea pig liver

1972 ◽  
Vol 261 (2) ◽  
pp. 315-320 ◽  
Author(s):  
Helen K. Berry ◽  
Roberta Cripps ◽  
Kay Nicholls ◽  
David McCandless ◽  
Calvin Harper
Keyword(s):  
Guinea Pig ◽  
Phenylalanine Hydroxylase ◽  
Hydroxylase Activity ◽  
Pig Liver ◽  
Guinea Pig Liver
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