scholarly journals The enzymic oxidation of glutathione in rat liver homogenates

1970 ◽  
Vol 117 (5) ◽  
pp. 947-949 ◽  
Author(s):  
P. C. Jocelyn
Keyword(s):  
Xanthine Oxidase ◽  
Rat Liver ◽  
Aerobic Oxidation ◽  
Liver Homogenate ◽  
Enzymic Oxidation ◽  
Liver Homogenates

1. The aerobic oxidation of GSH and other thiols by rat liver homogenate is abolished either by previous dialysis or by removal of the proteins but is restored by a mixture of the protein-free filtrate and the dialysed homogenate. 2. The oxidation is prevented by previously heating the dialysed homogenate but not the protein-free filtrate and also by known inhibitors of xanthine oxidase. 3. A similar oxidation occurs with hypoxanthine in place of of protein-free filtrate.

INHIBITION OF CHOLESTEROL FORMATION BY RAT LIVER HOMOGENATES

1955 ◽  
Vol 33 (2) ◽  
pp. 135-138 ◽  
Author(s):  
B. B. Migicovsky
Keyword(s):  
Vitamin A ◽  
Rat Liver ◽  
Cholesterol Synthesis ◽  
Liver Homogenate ◽  
Inhibitory Factor ◽  
Normal Rat ◽  
Liver Homogenates

The inability of liver homogenates, from starved and vitamin A deficient rats, to synthesize cholesterol is illustrated. A possible reason for this phenomenon is that these preparations inhibit cholesterol synthesis when added to a liver homogenate from a normal rat. The inhibitory factor or factors are present in both the supernate and residue portions of the homogenate, although the residue matter is more inhibitory.

scholarly journals Aqueous Extracts of Teucrium polium Possess Remarkable Antioxidant Activity In Vitro

2006 ◽  
Vol 3 (3) ◽  
pp. 329-338 ◽  
Author(s):  
Predrag Ljubuncic ◽  
Suha Dakwar ◽  
Irina Portnaya ◽  
Uri Cogan ◽  
Hassan Azaizeh ◽  
...  
Keyword(s):  
Lipid Peroxidation ◽  
Antioxidant Activity ◽  
Rat Liver ◽  
Antioxidant Properties ◽  
Liver Homogenate ◽  
Plasma Oxidation ◽  
Teucrium Polium ◽  
Liver Homogenates ◽  
Β Carotene

Teucrium poliumL. (Lamiaceae) (RDC 1117) is a medicinal plant whose species have been used for over 2000 years in traditional medicine due to its diuretic, diaphoretic, tonic, antipyretic, antispasmodic and cholagogic properties. The therapeutic benefit of medicinal plants is often attributed to their antioxidant properties. We previously reported that an aqueous extract of the leaves and stems of this plant could inhibit iron-induced lipid peroxidation in rat liver homogenate at concentrations that were not toxic to cultured hepatic cells. Others have reported that organic extracts of the aerial components of this plant could inhibit oxidative processes. Against this background, we felt further investigation on the antioxidant action of the extract ofT. poliumprepared according to traditional Arab medicine was warranted. Accordingly, we assessed (i) its ability to inhibit (a) oxidation of β-carotene, (b) 2,2′-azobis(2-amidinopropan) dihydrochloride (AAPH)-induced plasma oxidation and (c) iron-induced lipid peroxidation in rat liver homogenates; (ii) to scavenge the superoxide ($${\hbox{ O }}_{2}^{\bullet -}$$) radical and the hydroxyl radical (OH•); (iii) its effects on the enzyme xanthine oxidase activity; (iv) its capacity to bind iron; and (v) its effect on cell glutathione (GSH) homeostasis in cultured Hep G2 cells. We found that the extract (i) inhibited (a) oxidation of β-carotene, (b) AAPH-induced plasma oxidation (c) Fe2+-induced lipid peroxidation in rat liver homogenates (IC50 = 7 ± 2 μg ml−1); (ii) scavenged $${\hbox{ O }}_{2}^{\bullet -}$$(IC50 = 12 ± 3 μg ml−1) and OH• (IC50 = 66 ± 20 μg ml−1); (iii) binds iron (IC50 = 79 ± 17 μg ml−1); and (iv) tended to increase intracellular GSH levels resulting in a decrease in the GSSG/GSH ratio. These results demonstrate that the extract prepared from theT. poliumpossesses antioxidant activityin vitro. Further investigations are needed to verify whether this antioxidant effect occursin vivo.

Diminished hepatic triiodothyronine production in Gunn rats

1986 ◽  
Vol 113 (2) ◽  
pp. 281-288 ◽  
Author(s):  
J. R. Saltzman ◽  
D. W. Clark ◽  
R. D. Utiger
Keyword(s):  
Thyroid Hormone ◽  
Rat Liver ◽  
Liver Homogenate ◽  
Unconjugated Bilirubin ◽  
Thyroid Hormone Metabolism ◽  
Gunn Rats ◽  
Deiodinase Activity ◽  
Sediment Fraction ◽  
Liver Homogenates

Abstract. The liver is a major site of conversion of thyroxine (T4) to the more active thyroid hormone 3,5,3'-triiodothyronine (T3). Hepatic T4 to T3 conversion is altered by a variety of pathological processes and pharmacological agents. We studied T4 to T3 conversion in glucuronyl transferase deficient homozygous Gunn rats because they have a hepatic enzyme abnormality which leads to hyperbilirubinaemia, and also because they have been reported to have alterations in thyroid hormone metabolism. An in vitro incubation system employing the 10 000 × g supernatant of liver homogenate was used, and T3 production was measured by radioimmunoassay. Experiments were done using substrate concentrations ranging from 0.56 to 20 μm, tissue protein in concentrations ranging from 0.625 to 20 mg and incubation times of 15 to 60 min. T3 production by liver homogenates from homozygous Gunn rats in these studies ranged from 29 to 70% of that produced by liver homogenates from phenotypically normal heterozygous Gunn rats. The deficit in hepatic T3 production by homozygous rats could not be overcome by increasing cofactor concentrations. After ultracentrifugation at 100 000 μ g, T4-5'-deiodinase activity was found primarily in the 100 000 × g sediment fraction. Homogygous rat liver 100 000 × g sediment T3 production was 55% of that of the heterozygous rat liver 100 000 × g sediment. Liver cytosol from both homozygous and heterozygous rats inhibited microsomal T4-5'-deiodinase activity similarly. Addition of unconjugated bilirubin to liver homogenates resulted in reduction of T3 production in livers from both homozygous and heterozygous rats. Thus the diminished capacity for hepatic conversion of T4 to T3 in homozygous Gunn rats may be due to inhibition of T4-5'-deiodinase activity by high endogenous levels of unconjugated bilirubin.

scholarly journals The function of subcellular fractions in the oxidation of glutathione in rat liver homogenate

1970 ◽  
Vol 117 (5) ◽  
pp. 951-956 ◽  
Author(s):  
P. C. Jocelyn
Keyword(s):  
Uric Acid ◽  
Xanthine Oxidase ◽  
Rat Liver ◽  
Liver Homogenate ◽  
No Oxidation ◽  
Urate Oxidase ◽  
Supernatant Fraction ◽  
Endogenous Substrate ◽  
Additional Protein ◽  
Microsome Fraction

1. The aerobic loss of GSH added to the supernatant fraction from rat liver is much increased by including the microsome fraction, which both inhibits the concurrent reduction of the GSSG formed and also augments the net oxidation rate. 2. Oxidation occurs with a mixture of dialysed supernatant and a protein-free filtrate; the latter is replaceable by hypoxanthine and the former by xanthine oxidase, whereas fractions lacking this enzyme give no oxidation. 3. In all these instances augmentation occurs with microsomes, with fractions having urate oxidase activity and with the purified enzyme; uric acid and microsomes alone also support the oxidation. 4. Evidence implicating additional protein factors is discussed. 5. It is suggested that GSH oxidation by homogenate is linked through glutathione peroxidase to the reaction of endogenous substrate with supernatant xanthine oxidase and of the uric acid formed with peroxisomal urate oxidase.

INTRACELLULAR DISTRIBUTION OF PHOSPHOMONOESTERASES IN RAT LIVER HOMOGENATE

1954 ◽  
Vol 32 (1) ◽  
pp. 383-394 ◽  
Author(s):  
Claude Allard ◽  
Gaston de Lamirande ◽  
Hugo Faria ◽  
Antonio Cantero
Keyword(s):  
Acid Phosphatase ◽  
Rat Liver ◽  
Mouse Liver ◽  
Soluble Fraction ◽  
Liver Homogenate ◽  
Mitochondrial Fraction ◽  
Nuclear Fraction ◽  
Absolute Requirement ◽  
Rat Liver Cells ◽  
Liver Homogenates

Acid phosphatase or phosphomonoesterase II activity of rat and mouse liver homogenates, prepared in 0.25 M sucrose, was found mainly in the cytoplasmic granules. Since the small percentage of activity of the nuclear fraction activity could be explained by the presence of mitochondria (which were actually counted in this fraction) it is concluded that rat and mouse liver nuclei do not contain acid phosphatase activity.A rather broad range of acid phosphatase activity was observed in rat and mouse livers depending on the time elapsed between the preparation of homogenate and the activity determinations. However, a preincubation of the tissues or isolated fractions at 37° C. for 60 min. was sufficient to increase the activity to an optimal value, and thus eliminate variations due to the latency of this enzyme.Alkaline phosphatase or phosphomonoesterase I activity was also found to be latent in rat liver homogenates. The phenomenon was less apparent than for acid phosphatase and seemed to depend mostly on the nature of the buffer employed in the assay system.Some evidence for the presence of two forms of alkaline phosphatase in rat liver cells is presented. One form of the enzyme was found to have an absolute requirement of magnesium for activity and was present in the soluble fraction, whereas the other which was not activated by magnesium seemed firmly linked to the nuclei and microsomes and was absent in the soluble fraction. The activity in the mitochondrial fraction was small and seemed of doubtful significance.

INTRACELLULAR DISTRIBUTION OF PHOSPHOMONOESTERASES IN RAT LIVER HOMOGENATE

1954 ◽  
Vol 32 (4) ◽  
pp. 383-394 ◽  
Author(s):  
Claude Allard ◽  
Gaston de Lamirande ◽  
Hugo Faria ◽  
Antonio Cantero
Keyword(s):  
Acid Phosphatase ◽  
Rat Liver ◽  
Mouse Liver ◽  
Soluble Fraction ◽  
Liver Homogenate ◽  
Mitochondrial Fraction ◽  
Nuclear Fraction ◽  
Absolute Requirement ◽  
Rat Liver Cells ◽  
Liver Homogenates

Acid phosphatase or phosphomonoesterase II activity of rat and mouse liver homogenates, prepared in 0.25 M sucrose, was found mainly in the cytoplasmic granules. Since the small percentage of activity of the nuclear fraction activity could be explained by the presence of mitochondria (which were actually counted in this fraction) it is concluded that rat and mouse liver nuclei do not contain acid phosphatase activity.A rather broad range of acid phosphatase activity was observed in rat and mouse livers depending on the time elapsed between the preparation of homogenate and the activity determinations. However, a preincubation of the tissues or isolated fractions at 37° C. for 60 min. was sufficient to increase the activity to an optimal value, and thus eliminate variations due to the latency of this enzyme.Alkaline phosphatase or phosphomonoesterase I activity was also found to be latent in rat liver homogenates. The phenomenon was less apparent than for acid phosphatase and seemed to depend mostly on the nature of the buffer employed in the assay system.Some evidence for the presence of two forms of alkaline phosphatase in rat liver cells is presented. One form of the enzyme was found to have an absolute requirement of magnesium for activity and was present in the soluble fraction, whereas the other which was not activated by magnesium seemed firmly linked to the nuclei and microsomes and was absent in the soluble fraction. The activity in the mitochondrial fraction was small and seemed of doubtful significance.

scholarly journals A Colorimetric Assay for Xanthine Oxidase in Rat Liver Homogenates

1953 ◽  
Vol 200 (1) ◽  
pp. 303-310
Author(s):  
G. Litwack ◽  
J.W. Bothwell ◽  
J.N. Williams ◽  
C.A. Elvehjem
Keyword(s):  
Xanthine Oxidase ◽  
Rat Liver ◽  
Colorimetric Assay ◽  
Liver Homogenates

scholarly journals STUDIES ON ISOLATED CELL COMPONENTS

1951 ◽  
Vol 34 (5) ◽  
pp. 647-656 ◽  
Author(s):  
Norman G. Anderson ◽  
Karl M. Wilbur
Keyword(s):  
Rat Liver ◽  
High Speed ◽  
Sucrose Solution ◽  
Anticoagulant Activity ◽  
Liver Homogenate ◽  
Viscosity Increase ◽  
Cell Components ◽  
Liver Homogenates ◽  
Concentration Threshold ◽  
Isolated Cell

1. The addition of heparin to rat liver, kidney, or brain nuclei has been found to bring about the release of a gel. Chemical analysis and histochemical studies on whole homogenates and isolated nuclei demonstrated that the material released by heparin contained desoxyribonucleic acid (DNA) and protein. The action of heparin on nuclei is interpreted as the result of a combination with the basic proteins of the nucleus with a consequent displacement of DNA. 2. The addition of heparin to a finely divided dilute liver homogenate prepared in a phosphate-sucrose solution at pH 7.1 brings about a marked increase in viscosity which reaches a maximum in 6 to 8 minutes at 23° and then declines. 3. The concentration threshold for the viscosity effect was 0.1 mg. per 100 mg. fresh rat liver, with further increases in viscosity at higher heparin concentrations. Over a period of several hours a marked decrease in response to heparin was observed in homogenates stored at 0°. 4. Fractionation of the homogenate demonstrated that the viscosity increase was due to the presence of the nuclei alone, other components showing no effect. Microscopic observation showed that the increase in viscosity was associated with the appearance of a clear gel around nuclei treated with heparin. 5. Heparin brought about the release of DNA from the nuclei of incubated rat liver, kidney, and brain homogenates. In some instances over half the DNA is found in the supernatant after high speed centrifugation (20 minutes, 21,000 x g). 6. No correlation was found between anticoagulant activity of heparin preparations and their effectiveness in causing an increase in the viscosity of liver homogenates. Desulfated heparin produced none of the results described here for heparin.

Intensification of the xanthine oxidase activity of rat liver homogenates on storage

1968 ◽  
Vol 46 (9) ◽  
pp. 1047-1056
Author(s):  
D. G. R. Blair ◽  
B. D. McLennan
Keyword(s):  
Xanthine Oxidase ◽  
Rat Liver ◽  
Oxidase Activity ◽  
Enzyme Assay ◽  
Substrate Inhibition ◽  
Temperature Dependent ◽  
Xanthine Oxidase Activity ◽  
Aging Period ◽  
Liver Homogenates ◽  
High Concentrations

The xanthine oxidase activity of rat liver homogenates increased severalfold when the homogenates were stored (aged) at 4 °C for several days. The increase could be demonstrated by measuring xanthine oxidase activity by xanthine utilization or allantoin formation from xanthine. The increase in activity was not correlated with the concentrations of allantoin, uric acid, xanthine, or hypoxanthine in the homogenates, and, therefore, is not attributed to decrease of substrate inhibition, but its demonstration was partially inhibited by relatively high concentrations of xanthine in the enzyme-assay reaction medium.The increase in xanthine oxidase activity was temperature-dependent and was unaffected by the presence of glucose or adenosine 5′-triphosphate. Lysis of unbroken cells during the aging period and microbial contamination were not contributory. Dialysis of a fresh homogenate partially inhibited the increase in activity, but the addition of the dialysate of an aging homogenate to a dialyzed or fresh homogenate did not stimulate activity.The mechanism of the increase in xanthine oxidase activity has not been elucidated, but the fact that stimulation of the activity by methylene blue decreases as the homogenates age, suggests that the rate at which reduced xanthine oxidase is oxidized by air may increase with homogenate aging.

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