scholarly journals Factors affecting the premature induction of phosphopyruvate carboxylase in neonatal rat liver

1968 ◽  
Vol 108 (2) ◽  
pp. 325-331 ◽  
Author(s):  
D. Yeung ◽  
I. T. Oliver
Keyword(s):  
Rat Liver ◽  
Actinomycin D ◽  
Blood Glucose Concentration ◽  
Enzyme Synthesis ◽  
Neonatal Rat ◽  
Carboxylase Activity ◽  
Factors Affecting ◽  
Glucose Injection ◽  
Enzyme Development ◽  
Amino Acid Analogues

1. Phosphopyruvate carboxylase activity rapidly appears in the liver of prematurely delivered rats and development of activity is prevented by injection of actinomycin D just before delivery. 2. The activity is considerably decreased by puromycin and amino acid analogues and thus appears to be due to enzyme synthesis. 3. Newborn or premature animals show a transient intense phase of hypoglycaemia after delivery. 4. When the hypoglycaemic phase is prevented by glucose injection little phosphopyruvate carboxylase activity appears in the liver, but galactose, mannose and fructose, which have no effect on the blood glucose concentration, also repress enzyme development. 5. Lactate, pyruvate and glycerol injections repress the premature development of phosphopyruvate carboxylase. 6. Injections of glucagon, adrenalin and noradrenalin into the rat foetus in utero result in development of phosphopyruvate carboxylase activity. 7. These findings are discussed in relation to the mechanism of initiation of enzyme synthesis in neonatal rat liver.

Regulation of Enzyme Development for Glycerol Utilization by Neonatal Rat Liver

Neonatology ◽  
1973 ◽  
Vol 23 (5-6) ◽  
pp. 403-413 ◽  
Author(s):  
Jane Ward ◽  
D.G. Walker
Keyword(s):  
Rat Liver ◽  
Neonatal Rat ◽  
Enzyme Development ◽  
Glycerol Utilization

scholarly journals Development of gluconeogenesis in neonatal rat liver. Effect of premature delivery

1967 ◽  
Vol 105 (3) ◽  
pp. 1229-1233 ◽  
Author(s):  
D. Yeung ◽  
I. T. Oliver
Keyword(s):  
Rat Liver ◽  
Pyruvate Carboxylase ◽  
Neonatal Rat ◽  
Assay Method ◽  
Premature Delivery ◽  
Carboxylase Activity ◽  
Significant Linear Correlation ◽  
Foetal Rat ◽  
Rapid Appearance

1. An assay method for the determination of phosphopyruvate carboxylase activity is described in which improved sensitivity is obtained by separation of the enzyme from interfering pyruvate kinase by zone sedimentation. 2. The molecular weight of rat liver phosphopyruvate carboxylase determined by zone sedimentation is about 68000. 3. Premature delivery of rat foetuses by uterine section results in the rapid appearance of phosphopyruvate carboxylase, but hexose diphosphatase and pyruvate carboxylase, already present in the foetal rat liver, are not significantly affected, and glucose 6-phosphatase activity is only slightly affected. 4. The rate of incorporation of [14C]pyruvate into glucose by liver slices is also greatly increased by premature delivery and there is a highly significant linear correlation between this process and the phosphopyruvate carboxylase activity.

scholarly journals Development of gluconeogenesis in neonatal rat liver. Effect of triamcinolone

1967 ◽  
Vol 105 (3) ◽  
pp. 1219-1227 ◽  
Author(s):  
D. Yeung ◽  
R. S. Stanley ◽  
I. T. Oliver
Keyword(s):  
Rat Liver ◽  
Pyruvate Carboxylase ◽  
Normal Activity ◽  
Neonatal Rat ◽  
Transferase Activity ◽  
Carboxylase Activity ◽  
Period 2 ◽  
Foetal Rat ◽  
Significant Depression ◽  
Phosphofructokinase Activity

1. The normal development of the key enzymes of gluconeogenesis in rat liver, glucose 6-phosphatase, hexose diphosphatase, phosphopyruvate carboxylase and pyruvate carboxylase, was measured during the neonatal period. 2. Glucose 6-phosphatase, hexose diphosphatase and pyruvate carboxylase are all present in the late foetal liver, but all the enzymes show an increase in activity after birth. 3. Phosphopyruvate carboxylase is not present in liver extracts from foetal rats, but activity appears immediately after birth and increases rapidly over the first day and then more slowly to reach its maximum at the fourth postnatal day. 4. The fluorinated synthetic glucocorticoid, triamcinolone, was administered to foetal rats at various gestation times by intraperitoneal injection in utero and the animals were killed at intervals between 4 and 48hr. later. 5. The administration of triamcinolone results in slight depression of glucose 6-phosphatase, and a more significant depression of hexose diphosphatase to about one-half its normal activity in foetal rat liver. 6. Triamcinolone injection is without effect on pyruvate carboxylase activity and does not result in premature appearance of phosphopyruvate carboxylase in foetal rat liver. 7. Pyruvate kinase and aspartate amino-transferase activities in foetal rat liver are both depressed by triamcinolone treatment, whereas phosphofructokinase activity is elevated. 8. Tyrosine amino-transferase activity in foetal rat liver is markedly elevated in animals exposed to triamcinolone for 10hr. or more, but the effect is only observed in animals close to term. 9. The results are discussed in relation to mechanisms involved in the initial synthesis of tissue-specific enzymes in developing tissues, and it is concluded that glucocorticoids do not initiate the synthesis of the gluconeogenic enzymes.

scholarly journals Phosphopyruvate carboxylase induction by l-tryptophan. Effects on synthesis and degradation of the enzyme

1973 ◽  
Vol 136 (2) ◽  
pp. 259-264 ◽  
Author(s):  
F. J. Ballard ◽  
M. F. Hopgood
Keyword(s):  
Enzyme Activity ◽  
Specific Antibody ◽  
Actinomycin D ◽  
Relative Rate ◽  
Enzyme Synthesis ◽  
Enzyme Protein ◽  
Carboxylase Activity ◽  
Twofold Increase ◽  
Synthesis And Degradation

1. The administration of l-tryptophan to fed rats produces a twofold increase in hepatic phosphopyruvate carboxylase activity that represents a comparable increase in enzyme protein. With specific antibody against the enzyme we have shown that the increase in phosphopyruvate carboxylase is partially mediated via an actinomycin D-sensitive increase in enzyme synthesis. 2. In starved animals tryptophan increases the enzyme activity without any change in the relative rate of phosphopyruvate carboxylase synthesis. In this condition degradation of the enzyme is retarded by tryptophan by a mechanism that is not prevented by cycloheximide.

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.

Glucose repression and induction of enzyme synthesis in rat liver

1964 ◽  
Vol 2 ◽  
pp. 237-247 ◽  
Author(s):  
Henry C. Pitot ◽  
Carl Peraino ◽  
Nancy Pries ◽  
Alfred L. Kennan
Keyword(s):  
Rat Liver ◽  
Glucose Repression ◽  
Enzyme 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 Chain extension of ribonucleic acid by enzymes from rat liver cytoplasm

1968 ◽  
Vol 109 (4) ◽  
pp. 485-494 ◽  
Author(s):  
N. M. Wilkie ◽  
R. M. S. Smellie
Keyword(s):  
Rat Liver ◽  
Alkaline Hydrolysis ◽  
Actinomycin D ◽  
Chain Extension ◽  
Supernatant Fraction ◽  
Inorganic Pyrophosphate ◽  
Optimum Ph ◽  
Microsome Fraction ◽  
Hydrolysis Of ◽  
Generating System

1. The 105000g supernatant fraction of rat liver catalyses the incorporation of ribonucleotides from ribonucleoside triphosphates into polyribonucleotide material. The reaction requires Mg2+ ions and is enhanced by the addition of an ATP-generating system and RNA, ATP, UTP and CTP but not GTP are utilized in this reaction. In the case of UTP, the product is predominantly a homopolymer containing 2–3 uridine residues, and there is evidence that these may be added to the 3′-hydroxyl ends of RNA or oligoribonucleotide primers. 2. The microsome fraction of rat liver incorporates ribonucleotides from ATP, GTP, CTP and UTP into polyribonucleotide material. This reaction requires Mg2+ ions and is enhanced slightly by the addition of an ATP-generating system, and by RNA but not DNA. Supplementation of the reaction mixture with the three complementary ribonucleoside 5′-triphosphates greatly increases the utilization of a single labelled ribonucleoside 5′-triphosphate. The optimum pH is in the range 7·0–8·5, and the reaction is strongly inhibited by inorganic pyrophosphate and to a much smaller degree by inorganic orthophosphate. It is not inhibited by actinomycin D or by deoxyribonuclease. In experiments with [32P]UTP in the absence of ATP, GTP and CTP, 80–90% of 32P was recovered in UMP-2′ or −3′ after alkaline hydrolysis of the reaction product. When the reaction mixture was supplemented with ATP, GTP and CTP, however, about 40% of the 32P was recovered in nucleotides other than UMP-2′ or −3′. Although the reactions seem to lead predominantly to the synthesis of homopolymers, the possibility of some formation of some heteropolymer is not completely excluded.

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.

Factors Affecting the Rate of Gluconeogenesis from L-Cysteine in the Perfused Rat Liver

1976 ◽  
Vol 106 (9) ◽  
pp. 1272-1278 ◽  
Author(s):  
Ronald C. Simpson ◽  
Richard A. Freedland
Keyword(s):  
Rat Liver ◽  
Perfused Rat Liver ◽  
Factors Affecting
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