Subcellular localization of 7-glutamyltransferase activity in guinea pig liver. Effect of phenobarbital on the enzyme activity levels

1. The subcellular distribution of endogenous folate and of injected [3H]folic acid has been studied in guinea-pig liver. 2. Endogenous folate was found to be concentrated in the mitochondrial and cell-sap fractions. 3. At 1 h after injection, labelled folic acid (pteroylglutamic acid) was concentrated in the microsomes (where it is possibly reduced to tetrahydrofolic acid). 4. At all subsequent times after injection of labelled pteroylglutamic acid (4, 24 and 84 h) radioactivity was concentrated in mitochondria and cell sap and it is, therefore, likely that conjugation of glutamates to form pteroylpolyglutamates occurs in one or both of these subcellular fractions in mammalian cells. 5. Methotrexate-treated animals converted at least some labelled pteroylglutamic acid into non-reduced pteroyl di-, tri- and poly-glutamic acids by 4 h after the injection. 6. Reduction of pteroylglutamic acid is, therefore, not essential for pteroylpolyglutamate formation in liver cells. 7. Methotrexate blocks the reduction of pteroyl di-, tri- and poly-glutamic acids, as well as of pteroylglutamic acid.

Download Full-text

Ontogeny of guinea pig liver cholesterol 7α-hydroxylase: Unexpected inverse correlation of enzyme activity with expanding bile acid pool

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(85)91189-1 ◽

1985 ◽

Vol 132 (2) ◽

pp. 702-707 ◽

Cited By ~ 3

Author(s):

R.L. Yunker ◽

M.T.R. Subbiah

Keyword(s):

Enzyme Activity ◽

Bile Acid ◽

Guinea Pig ◽

Inverse Correlation ◽

Liver Cholesterol ◽

Bile Acid Pool ◽

Pig Liver ◽

Acid Pool ◽

Guinea Pig Liver

Download Full-text

Factors affecting the 16α-hydroxylation of estrone 3-sulfate by guinea pig liver microsomes

Canadian Journal of Biochemistry ◽

10.1139/o81-063 ◽

1981 ◽

Vol 59 (6) ◽

pp. 454-460 ◽

Cited By ~ 8

Author(s):

C. J. Tsoulis ◽

R. Hobkirk

Keyword(s):

Enzyme Activity ◽

Cytochrome P450 ◽

Guinea Pig ◽

Liver Microsomes ◽

Pig Liver ◽

Factors Affecting ◽

Fourfold Increase ◽

Brij 35 ◽

Guinea Pig Liver Microsomes ◽

Guinea Pig Liver

The estrone 3-sulfate 16α-hydroxylase of guinea pig liver microsomes has been demonstrated to be sensitive to CO. A CO/O2 ratio of 0.64 caused 50% inhibition of activity. Since inhibition was also obtained in the presence of 2-diethylaminoethyl-2,2-diphenylvalerate∙HCl it seems likely that the hydroxylase is a cytochrome P450 containing system. A fourfold increase in enzyme activity was brought about by 40 mM Mg2+ or Ca2+ while the same concentration of Mn2+ resulted in a twofold increase. Lesser increases were seen with Na+ or K+ and complete inhibition was obtained in the presence of Fe2+, Cu2+, or EDTA. When assayed in the presence of detergent concentrations sufficiently small to guard against cytochrome P450 destruction, it was found that Cutscum, Triton X-100, and Triton N-101 each caused greatest inhibition of enzyme activity. Lesser inhibition was apparent in the presence of Miranol H2M, cholate, or deoxycholate. The nonionic detergent, Brij 35, caused least inhibition of all and, when hepatic microsomes were treated with higher concentrations of Brij 35, about 80% of protein and over 95% cytochrome P450 were to be found in the 100 000 × g supernatant. Microsomal activity was more stable when stored at −20 °C in buffer containing glycerol, EDTA, and dithiothreitol than in buffer alone. Under best conditions only 10% of the hydroxylase activity was lost in one week.

Download Full-text

Die Bedeutung der Homogenisationsart und -intensität für die Größe und Konstanz der Sauerstoffaufnahme von Meerschweinchen-Leberhomogenat / The Influence of Mode and Intensity of Homogenization on the Absolute Value and Stability of Oxygen Consumption of Guinea Pig Liver Homogenates

Zeitschrift für Naturforschung C ◽

10.1515/znc-1977-11-1205 ◽

1977 ◽

Vol 32 (11-12) ◽

pp. 908-912 ◽

Cited By ~ 5

Author(s):

H. J. Schmidt ◽

U. Schaum ◽

J. P. Pichotka

Keyword(s):

Oxygen Uptake ◽

Guinea Pig ◽

Measuring Time ◽

Pig Liver ◽

Absolute Value ◽

Modified Method ◽

Simultaneous Measurements ◽

Liver Homogenates ◽

The Absolute ◽

Guinea Pig Liver

Abstract The influence of five different methods of homogenisation (1. The method according to Potter and Elvehjem, 2. A modification of this method called Potter S, 3. The method of Dounce, 4. Homogenisation by hypersonic waves and 5. Coarce-grained homogenisation with the “Mikro-fleischwolf”) on the absolute value and stability of oxygen uptake of guinea pig liver homogenates has been investigated in simultaneous measurements. All homogenates showed a characteristic fall of oxygen uptake during measuring time (3 hours). The modified method according to Potter and Elvehjem called Potter S showed reproducible results without any influence by homogenisation intensity.

Download Full-text

Precision-cut Guinea-pig Liver Slices as a Tool for Studying the Toxicity of Volatile Anaesthetics

Alternatives to Laboratory Animals ◽

10.1177/026119299001800120.1 ◽

1990 ◽

Vol 18 (1_part_1) ◽

pp. 191-199

Author(s):

Hanan N. Ghantous ◽

Jeanne Fernando ◽

Scott E. Morgan ◽

A. Jay Gandolfi ◽

Klaus Brandel

Keyword(s):

Guinea Pig ◽

Rank Order ◽

Normal Liver ◽

Liver Slice ◽

Volatile Anaesthetics ◽

Pig Liver ◽

Liver Slices ◽

Guinea Pig Liver ◽

Krebs Henseleit Buffer

Cultured precision-cut liver slices retain normal liver architecture and physiological biochemical functions. Hartley male guinea-pig liver slices have proven to be a good model for studying the biotransformation and toxicity of halothane. This system was used to evaluate the biotransformation and toxicity of different volatile anaesthetics (halothane, enflurane, isoflurane and sevoflurane), and compare their effects to those of new anaesthetics (desflurane). Liver slices (250–300μm thick) were incubated in sealed roller vials, containing Krebs Henseleit buffer at 37°C under 95% O2:5% CO2 atmosphere. Volatile anaesthetics were delivered by volatilisation after pre-incubation for 1 hour to produce a constant concentration in the medium. Production of the metabolites, trifluroacetic acid and fluoride ion, was measured. Intracellular potassium ion content, protein synthesis and secretion were determined as indicators of viability of the slices. The rank order of biotransformation of anaesthetics by the liver slices was halothane >sevoflurane>isoflurane and enflurane>desflurane. The rank order of hepatotoxicity of these anaesthetics was halothane>isoflurane and enflurane>sevoflurane and desflurane. Halothane is the anaesthetic which is metabolised furthest and has the most toxic effect, while desflurane is the least metabolised anaesthetic and has the least toxicity. This in vitro cultured precision-cut liver slice system appears to be suitable for studying the biotransformation of volatile anaesthetics and correlating its role in the resulting toxicity.

Download Full-text