scholarly journals Alteration of enzyme activity in rat liver following the acute and chronic administration of nicotine

1970 ◽  
Vol 16 (3) ◽  
pp. 613-625 ◽  
Author(s):  
R.W. Ruddon ◽  
A.M. Cohen
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Chronic Administration

Effect of saturated fat diets on rat liver NADP-linked enzymes

1965 ◽  
Vol 209 (4) ◽  
pp. 773-780 ◽  
Author(s):  
Helen M. Tepperman ◽  
Jay Tepperman
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Rat Liver ◽  
Corn Oil ◽  
Saturated Fat ◽  
Coconut Oil ◽  
Liver Slices ◽  
Fat Diets ◽  
Effect Of Feeding

The aggregate hexosemonophosphate dehydrogenase (HMPD) activity was found to be higher in livers of rats fed a diet containing saturated fat (hydrogenated coconut oil = H) for 7 days and fasted for 48 hr than it was in similarly prepared animals fed a corn oil (CO) diet. Later, a liver HMPD-increasing effect of feeding H was found in nonfasted animals. Lipogenesis (i.e., the incorporation of acetate-1-C14 into fatty acids by liver slices) was shown to be as low or lower in the H group as in the CO. Liver slices prepared from H and CO diet adapted rats were incubated with either acetate-1-C14 or palmitate-1-C14 and the extent of incorporation of C14 into individual fatty acids was measured. With both substrates more radioactivity was found in 16:1, 18:0, and 18:1 in the case of H-fed animals. It is proposed that a component of the signal for eliciting increased NADP-linked enzyme activity in the H rats was an increased rate of oxidation of NADPH attendant on monoene formation and chain lengthening.

Glucocorticoid effects on respiration and metabolism by rat liver homogenates

1962 ◽  
Vol 202 (2) ◽  
pp. 343-346 ◽  
Author(s):  
Dennis D. Goetsch ◽  
L. E. McDonald
Keyword(s):  
Lactic Acid ◽  
Oxygen Uptake ◽  
Rat Liver ◽  
Inorganic Phosphate ◽  
Chronic Administration ◽  
Glucocorticoid Treatment ◽  
Carbohydrate Utilization ◽  
Protein Levels ◽  
Liver Homogenates ◽  
And Control

The effects of glucocorticoid administration on oxygen uptake, glucose and glycogen disappearance, lactic acid formation, and inorganic phosphate and protein levels in rat liver homogenates have been studied. A single injection of hydrocortisone, prednisolone, or 9 α-fluoroprednisolone 5 hr before sacrifice resulted in a highly significant increase in oxygen uptake by rat liver homogenates, whereas chronic administration of prednisolone daily for 7 days caused a marked inhibition in homogenate respiration. Glycolytic rate did not appear to be affected by single injections since endogenous carbohydrate utilization was similar in liver homogenates prepared from control and treated animals. Incubation of liver homogenates under aerobic conditions disclosed that inorganic phosphate levels were decreased in homogenates from corticoid-treated rats, whereas these levels were similar in treated and control liver homogenates incubated under nitrogen. Under anaerobic conditions, liver homogenates from treated rats accumulated lactic acid more rapidly than untreated liver homogenates. Glucocorticoid treatment did not appear to affect protein disappearance since no differences between protein levels in treated and untreated rat liver homogenates were detected following incubation.

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 Induction of carnitine acetyltransferase by clofibrate in rat liver

1981 ◽  
Vol 194 (1) ◽  
pp. 249-255 ◽  
Author(s):  
B Mittal ◽  
C K R Kurup
Keyword(s):  
Protein Synthesis ◽  
Enzyme Activity ◽  
Rat Liver ◽  
Time Lag ◽  
Mitochondrial Protein ◽  
Carnitine Acetyltransferase ◽  
Enzyme Protein ◽  
General Protein Synthesis ◽  
Liver And Kidney ◽  
General Protein

Administration of the anti-hypercholesterolaemic drug clofibrate to the rat increases the activity of carnitine acetyltransferase (acetyl-CoA-carnitine O-acetyltransferase, EC 2.3.1.7) in liver and kidney. The drug-mediated increase in enzyme activity in hepatic mitochondria shows a time lag during which the activity increases in the microsomal and peroxisomal fractions. The enzyme induced in the particulate fractions is identical with one normally present in mitochondria. The increase in enzyme activity is prevented by inhibitors of RNA and general protein synthesis. Mitochondrial protein-synthetic machinery does not appear to be involved in the process. Immunoprecipitation shows increased concentration of the enzyme protein in hepatic mitochondria isolated from drug-treated animals. In these animals, the rate of synthesis of the enzyme is increased 7-fold.

scholarly journals Properties of cytosolic components activating rat hepatic 5-deiodination in the presence of NADPH

1986 ◽  
Vol 234 (2) ◽  
pp. 391-398 ◽  
Author(s):  
K Sawada ◽  
B C W Hummel ◽  
P G Walfish
Keyword(s):  
Enzyme Activity ◽  
Glutathione Reductase ◽  
Rat Liver ◽  
Column Chromatography ◽  
Reduced Glutathione ◽  
Hydrogen Acceptor ◽  
Simultaneous Addition ◽  
Heat Stable ◽  
Hepatic Microsomes ◽  
Normal Rat

The effects of cytosol, NADPH and reduced glutathione (GSH) on the activity of 5′-deiodinase were studied by using washed hepatic microsomes from normal fed rats. Cytosol alone had little stimulatory effect on the activation of microsomal 5′-deiodinase. NADPH had no stimulatory effect on the microsomal 5′-deiodinase unless cytosol was added. 5′-deiodinase activity was greatly enhanced by the simultaneous addition of NADPH and cytosol (P less than 0.001); this was significantly higher than that with either NADPH or cytosol alone (P less than 0.001). GSH was active in stimulating the enzyme activity in the absence of cytosol, but the activity of 5′-deiodinase with 62 microM-NADPH in the presence of cytosol was significantly higher than that with 250 microM-GSH in the presence of the same concentration of cytosol (P less than 0.001). The properties of the cytosolic components essential for the NADPH-dependent activation of microsomal 5′-deiodinase independent of a glutathione/glutathione reductase system were further assessed using Sephadex G-50 column chromatography to yield three cytosolic fractions (A, B and C), wherein A represents pooled fractions near the void volume, B pooled fractions of intermediate Mr (approx. 13 000), and C of low Mr (approx. 300) containing glutathione. In the presence of NADPH (1 mM), the 5′-deiodination rate by hepatic washed microsomes is greatly increased if both A and B are added and is a function of the concentrations of A, B, washed microsomes and NADPH. A is heat-labile, whereas B is heat-stable and non-dialysable. These observations provide the first evidence of an NADPH-dependent cytosolic reductase system not involving glutathione which stimulates microsomal 5′-deiodinase of normal rat liver. The present data are consistent with a deiodination mechanism involving mediation by a reductase (other than glutathione reductase) in fraction A of an NADPH-dependent reduction of a hydrogen acceptor in fraction B, followed by reduction of oxidized microsomal deiodinase by the reduced acceptor (component in fraction B).

scholarly journals The effects of acetate, metal cations, phenobarbitone, porphyrogens and substrates of glycine acyltransferase on the utilization of haem by rat liver apo-(tryptophan pyrrolase)

1977 ◽  
Vol 164 (2) ◽  
pp. 431-438 ◽  
Author(s):  
A A B Badawy
Keyword(s):  
Enzyme Activity ◽  
Rat Liver ◽  
Metal Cations ◽  
Oxygenase Activity ◽  
Tryptophan Pyrrolase ◽  
Haem Oxygenase ◽  
Activity Enhancement

1. The utilization of haem by rat liver apo-(tryptophan pyrrolase) under basal conditions and after enhancement of the enzyme activity by various mechanisms was studied under the influence of treatments affecting various aspects of liver haem metabolism. 2. These treatments were: benzoate and p-aminobenzoate as substrates of glycine acyltransferase, acetate as an inhibitor of 5-aminolaevulinate synthase activity, enhancement of 5-aminolaevulinate dehydratase by aluminium, destruction of haem and inhibition of ferrochelatase by porphyrogens, increased haem utilization by phenobarbitone and enhancement of haem oxygenase activity by metal cations. 3. The results show that the haem saturation of the apoenzyme is sensitive to all these treatments. 4. The possible usefulness of tryptophan pyrrolase in studying the regulation of liver haem is suggested.

Purification of p-hydroxyphenylpyruvate hydroxylase from rat liver—requirements for cofactors

1976 ◽  
Vol 54 (5) ◽  
pp. 423-431 ◽  
Author(s):  
Kun-Tsan Lin ◽  
John C. Crawhall
Keyword(s):  
Molecular Weight ◽  
Enzyme Activity ◽  
Rat Liver ◽  
Gel Filtration ◽  
Protein Band ◽  
Final Concentration ◽  
Assay Method ◽  
Enzyme Extract ◽  
Crude Enzyme Extract ◽  
Single Protein

Theenzyme p-hydroxyphenylpyruvate hydroxylase (EC 1.13.11.27)from rat liver was studied with the assay method which measures the release of 14CO2 from p-hydroxyphenyl [carboxyl-,14C]pyruvate. Extensive dialysis of the crude enzyme extract against Tris buffer or purification involving ammonium sulfate, gel filtration, and ion exchange results in loss of enzyme activity that can be reactivated by Fe2+, dichlorophenolindophenol, and various other agents. The effect of these activators depends critically on their final concentration in the assay media.A 70-fold purification of the enzyme fraction yielded a preparation which behaved as a single protein band in Sephadex G-150. It had an isoelectric point at 5.85 and molecular weight of 63 000. The enzyme obtained appears to be different in some respects from those described by other workers from the liver of dog, human, chicken, and frog.

scholarly journals Validation of an HPLC Method for the Simultaneous Quantification of Metabolic Reaction Products Catalysed by CYP2C11 Enzymes in Rat Liver Microsomes: In Vitro Inhibitory Effect of Salicylic Acid on CYP2C11 Enzyme

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4294 ◽  
Author(s):  
Salhab ◽  
Naughton ◽  
Barker
Keyword(s):  
High Performance Liquid Chromatography ◽  
Enzyme Activity ◽  
Salicylic Acid ◽  
Liquid Chromatography ◽  
Rat Liver ◽  
High Performance ◽  
Inhibitory Effect ◽  
Metabolic Reaction ◽  
Rat Liver Microsomes

The inhibitory effect of new chemical entities on rat liver P450 marker activities was investigated in a functional approach towards drug development. Treatment of colorectal cancer (CRC) and chemoprevention using salicylic acid has gained a lot of attention, mainly in the prevention of the onset of colon cancer. Thus, an in vitro inhibitory effect of salicylic acid on rat CYP2C11 activity was examined by using high performance liquid chromatography (HPLC). High performance liquid chromatography analysis of a CYP2C11 assay was developed on a reversed phase C18 column (SUPELCO 25 cm × 4.6 mm × 5 µm) at 243 nm using 32% phosphate buffer (pH 3.36) and 68% methanol as a mobile phase. The CYP2C11 assay showed good linearity for all components (R2 > 0.999). Substrates and metabolites were found to be stable for up to 72 hours. Additionally, the method demonstrated good reproducibility, intra- and inter-day precision (<15%), acceptable recovery and accuracy (80%–120%), and low detection (1.3501 µM and 3.2757 µM) and quantitation limit values (4.914 µM and 9.927 µM) for 16α-hydroxytestosterone and testosterone, respectively. Salicylic acid acts reversibly as a noncompetitive (weak) inhibitor with Ki = 84.582 ± 2.67 µM (concentration of inhibitor to cause 50% inhibition of original enzyme activity (IC50) = 82.70 ± 2.67 µM) for CYP2C11 enzyme activity. This indicates a low potential to cause toxicity and drug–drug interactions.

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