scholarly journals Cholesterol 7α-hydroxylase in rat liver microsomal preparations

1972 ◽  
Vol 128 (1) ◽  
pp. 1-9 ◽  
Author(s):  
K. A. Mitropoulos ◽  
S. Balasubramaniam
Keyword(s):  
Fatty Acids ◽  
Molecular Oxygen ◽  
Rat Liver ◽  
Main Product ◽  
Subcellular Fractions ◽  
Native Protein ◽  
Low Concentrations ◽  
Rat Livers ◽  
Double Isotope

Subcellular fractions containing microsomes prepared from rat livers homogenized in the absence of EDTA catalysed the oxidation of cholesterol to 7α-hydroxycholesterol, 7-oxocholesterol, 7β-hydroxycholesterol and 5α-cholestane-3β,5,6β-triol. These reactions required native protein, molecular oxygen and NADPH. It is suggested that these compounds are formed by a peroxidation analogous to the peroxidation of fatty acids catalysed by liver microsomal preparations. Incubations of [4-14C]cholesterol with microsomal preparations from rat liver homogenized in the presence of EDTA gave 7α-hydroxy[14C]cholesterol as the main product. This reaction required molecular oxygen and NADPH, and was inhibited by CO. The mass of 7α-hydroxycholesterol formed during the incubation was measured by a double-isotope-derivative dilution procedure. This procedure was used to assay the activity of cholesterol 7α-hydroxylase and to measure low concentrations of endogenous 7α-hydroxycholesterol in liver.

In Vitro Conjugation of Ethanolamine with Fatty Acids by Rat Liver Subcellular Fractions

2005 ◽  
Vol 68 (8) ◽  
pp. 667-676 ◽  
Author(s):  
Shagufta H. Khan ◽  
Bhupendra S. Kaphalia ◽  
G. A. S. Ansari
Keyword(s):  
Fatty Acids ◽  
Rat Liver ◽  
Subcellular Fractions

Hepatic uptake of intact glutathione S-conjugate, inhibition by organic anions, and sinusoidal catabolism

1993 ◽  
Vol 265 (3) ◽  
pp. G547-G554
Author(s):  
C. A. Hinchman ◽  
A. T. Truong ◽  
N. Ballatori
Keyword(s):  
Guinea Pig ◽  
Rat Liver ◽  
Marked Decrease ◽  
Hepatic Uptake ◽  
Half Time ◽  
High Concentrations ◽  
Rat Livers ◽  
Dose Dependent ◽  
Uptake And Metabolism ◽  
Guinea Pig Liver

To identify potential mechanisms for hepatic removal of circulating glutathione (GSH) conjugates, uptake and metabolism of S-2,4-dinitrophenylglutathione (DNP-SG) were examined in isolated perfused livers from rat and guinea pig. Guinea pig livers perfused with 5 mumol of DNP-SG in a recirculating system (50 microM initial concn) rapidly cleared the conjugate from the perfusate (half time 3.7 min), whereas clearance was considerably slower in rat liver (half time 35 min). Disappearance of DNP-SG from the perfusate was accompanied by a simultaneous appearance of DNP-SG and its metabolites in bile. Addition of acivicin, an inhibitor of gamma-glutamyltransferase (gamma-GT), to the perfusate resulted in a marked decrease in DNP-SG clearance by guinea pig liver but had no effect in rat liver, suggesting that in the guinea pig this process is largely dependent on sinusoidal gamma-GT activity. However, even in the presence of acivicin, rat and guinea pig livers removed nearly one-half of the administered DNP-SG from the recirculating perfusate over 30 min. High concentrations of DNP-SG were found in bile (up to 3.7 mM), indicating that the liver is capable of transporting the intact conjugate from the circulation. When rat livers were perfused with higher concentrations of DNP-SG (100 and 250 microM), biliary excretion of DNP-SG increased dose dependently, with concentrations in bile reaching 10 mM at the higher dose. This was accompanied by a dose-dependent choleresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of Slice Thickness and Culture Conditions on the Metabolism of 7-Ethoxycoumarin in Precision-cut Rat Liver Slices

1998 ◽  
Vol 26 (4) ◽  
pp. 541-548
Author(s):  
Roger J. Price ◽  
Anthony B. Renwick ◽  
Paula T. Barton ◽  
J. Brian Houston ◽  
Brian G. Lake
Keyword(s):  
Gas Phase ◽  
Rat Liver ◽  
Xenobiotic Metabolism ◽  
Culture Conditions ◽  
Slice Thickness ◽  
Dependent Manner ◽  
Sprague Dawley ◽  
Liver Slices ◽  
Sprague Dawley Rats ◽  
Rat Livers

This study investigated the effects of some experimental variables on the rate of xenobiotic metabolism in precision-cut rat liver slices. Liver slices of 123 ± 8μm (mean ± SEM of six slices), 165 ± 3μm, 238 ± 6μm and 515 ± 14μm thickness were prepared from male Sprague-Dawley rats, and incubated in RPMI 1640 medium in an atmosphere of 95% O2/5% CO2 by using a dynamic organ culture system. Liver slices of all thicknesses metabolised 10μM 7-ethoxycoumarin to total (free and conjugated) 7-hydroxycoumarin in a time-dependent manner. The rate of 7-ethoxycoumarin metabolism was greatest in 165μm thick slices and slowest in 515μm thick slices, being 2.74 ± 0.19pmol/minute/mg slice protein and 0.69 ± 0.07pmol/minute/mg slice protein, respectively. No marked effects on the rate of 7-ethoxycoumarin metabolism in liver slices were observed either by changing the medium to Earle's balanced salt solution (EBSS) or by changing the gas phase to 95% air/5% CO2. Moreover, the perfusion of rat livers with EBSS at 2–4°C, prior to preparation of tissue cores, did not enhance 7-ethoxycoumarin metabolism in rat liver slices. In this study, the optimal slice thickness was 175μm, with higher rates of 7-ethoxycoumarin metabolism being observed than with 250μm thick slices, which are often used for studies of xenobiotic metabolism. Variable results were obtained with slices of around 100–120μm thickness, which may be attributable to the ratio between intact hepatocytes and cells damaged by the slicing procedure in these very thin slices.

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