scholarly journals The catabolism of cholesterol in vitro. Formation of 3α,7α,12α-trihydroxy-5β-cholestanoic acid from cholesterol by rat liver

1969 ◽  
Vol 114 (1) ◽  
pp. 1-3 ◽  
Author(s):  
D. Mendelsohn ◽  
L. Mendelsohn
Keyword(s):  
Gall Bladder ◽  
Bile Acids ◽  
Rat Liver ◽  
Specific Radioactivity ◽  
Liver Preparation

1. Both 25-d- and 25-l-3α,7α,12α-trihydroxy-5β-cholestanoic acid were isolated from the gall-bladder bile of Crocodylus niloticus. 2. The catabolism of cholesterol to 25-d- and 25-l-3α,7α,12α-trihydroxy-5β-cholestanoic acid respectively was studied by using a rat liver preparation in vitro. The results show that rat liver can metabolize cholesterol to both forms of 3α,7α,12α-trihydroxy-5β-cholestanoic acid. However, a preference was noted for the formation from [4−14C]cholesterol of 3α,7α,12α-trihydroxy-5β-cholestanoic acid (25-d), which was isolated from the incubations with a specific radioactivity about four times that of 3α,7α,12α-trihydroxy-5β-cholestanoic acid (25-l). 3. The results indicate that 3α,7α,12α-trihydroxy-5β-cholestanoic acid is a normal intermediate in the biosynthesis of bile acids from cholesterol in the rat.

scholarly journals Biosynthesis of phosphatidylethanolamines and phosphatidylcholines from ethanolamine and choline in rat liver

1975 ◽  
Vol 146 (2) ◽  
pp. 309-315 ◽  
Author(s):  
R Sundler ◽  
B Akesson
Keyword(s):  
Rat Liver ◽  
Molecular Species ◽  
Kinetic Models ◽  
Quantitative Data ◽  
Specific Radioactivity ◽  
Similar Rate ◽  
Time Intervals ◽  
Previous Suggestion ◽  
Kinetics Of

1. The kinetics of phosphatidylcholine and phosphatidylethanolamine synthesis in rat liver were followed 5-60 min after the intraportal injection of [14-C]choline and [3-H]-ethanolamine. 2. At all time-intervals the specific radioactivity of CDP-choline was only about half that of phosphorylcholine. This indicated that CDP-choline was formed at a similar rate from phosphorylcholine and phosphatidylcholines, the latter probably through the reverse reaction of cholinephosphotransferase (EC 2.7.8.2.). In view of recent data obtained from experiments in vitro this implies a significant role for the cholinephosphotransferase reaction in the turnover of molecular species of phosphatidylcholine. 3. The specific radioactivity of CDP-ethanolamine was about twice that of phosphorylethanolamine at all time-intervals studied. This supports a previous suggestion that the liver phosphorylethanolamine pool is subject to compartmentation and shows that there is no rapid equilibration between different pools. In contrast with a recent study, no evidence was found for any significant methylation of phosphoryl-or CDP-ethanolamine to the corresponding choline derivative. 4. Quantitative data on the biosynthesis of molecular species of phosphoLIPIDS via CDP derivatives were calculated according to simple kinetic models. They were in the same range as those calculated from earlier data on precusors incorporated via diacylglycerols. 5. The proportion of radioactive phosphatidylethanolamines appearing in the plasma was approximately ten times lower than that for phosphatidylcholines. No selectivity was observed in the transfer into plasma of different molecular species of phosphatidylethanolamine.

The effects of cofactor and species differences on the in vitro metabolism of propiophenone and phenylacetone

1981 ◽  
Vol 59 (2) ◽  
pp. 195-201 ◽  
Author(s):  
R. T. Coutts ◽  
D. R. Prelusky ◽  
G. R. Jones
Keyword(s):  
Rat Liver ◽  
In Vitro Metabolism ◽  
Metabolic Route ◽  
Liver Preparation ◽  
Carbonyl Reduction ◽  
Alcohol Dehydrogenation ◽  
Liver Homogenates ◽  
A Minor ◽  
Minor Extent

In vitro metabolism of the aromatic ketone propiophenone and its nonaromatic isomer phenylacetone was studied using fortified 12 000 × g supernatants of liver homogenates from rat and rabbit. Reduction to the corresponding alcohols was the major metabolic route observed, although aliphatic C-hydroxylation and alcohol dehydrogenation also occurred. Marked differences were observed in the amounts of carbonyl reduction of the substrates, which was dependant on the species as well as the cofactor employed. Using rat liver preparation, phenylacetone was reduced to 1-phenyl-2-propanol much more efficiently with an NADH-fortified system than when NADPH was used whereas in rabbit, extensive reduction occurred in the presence of either cofactor. Reduction of propiophenone to 1-phenyl-1-propanol by rat liver preparation was slightly greater in the presence of NADH than with NADPH; the converse was observed in rabbit.Aliphatic hydroxylation of propiophenone to 2-hydroxy-1-phenyl-1-propamine was also a significant metabolic pathway in both species, with NADPH being the more efficient cofactor, but C-1 hydroxylation of phenylacetone to 1-hydroxy-1-phenyl-2-propanone occurred only to a minor extent. Small amounts of 1-phenyl-1,2-propanedione, as well as both erythro and threo isomers of 1-phenyl-1,2-propanediol, were also identified as metabolites in both species. Similar metabolic studies were carried out on the alcohols 1-phenyl-1-propanol and 1-phenyl-2-propanol and again the nature and quantities of metabolites isolated showed both species and cofactor dependancies.

scholarly journals The submicrosomal localization of acyl-coenzyme A–cholesterol acyltransferase and its substrate, and of cholesteryl esters in rat liver

1978 ◽  
Vol 174 (3) ◽  
pp. 863-872 ◽  
Author(s):  
Santhirasegaram Balasubramaniam ◽  
Soundararajan Venkatesan ◽  
Konstantinos A. Mitropoulos ◽  
Timothy J. Peters
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Microsomal Fraction ◽  
Smooth Endoplasmic Reticulum ◽  
Cholesterol Acyltransferase ◽  
Specific Radioactivity ◽  
Cholesteryl Esters ◽  
Distribution Profile

To determine the submicrosomal distribution of acyl-CoA–cholesterol acyltransferase and of cholesteryl esters, the microsomal fraction and the digitonin-treated microsomal preparation of rat liver were subjected to analytical centrifugation on sucrose density gradients. With untreated microsomal fractions the distribution profile and the median density of acyl-CoA–cholesterol acyltransferase were very similar to those of RNA. This is in contrast with hydroxymethylglutaryl-CoA reductase and cholesterol 7α-hydroxylase, which are confined to endoplasmic reticulum membranes with low ribosomal coating. In digitonin-treated microsomal preparations activity of acyl-CoA–cholesterol acyltransferase was not detectable. The labelling of untreated microsomal fractions with trace amounts of [14C]cholesterol followed by subfractionation of the labelled microsomal fraction showed that the specific radioactivity of cholesteryl esters obtained in vitro by the various subfractions was similar with all subfractions but different from the specific radioactivity of the 7α-hydroxycholesterol obtained in vitro by the same subfraction. These results demonstrate the existence of two pools of cholesterol confined to membranes from the endoplasmic reticulum, one acting as substrate for cholesterol 7α-hydroxylase and the other acting as substrate for acyl-CoA–cholesterol acyltransferase. The major part of cholesteryl esters present in both untreated and digitonin-treated microsomal fractions was distributed at densities similar to those of membranes from the smooth endoplasmic reticulum and at densities lower than those of smooth membranes from Golgi apparatus. The ratio of the concentrations of non-esterified to esterified cholesterol in the subfractions from both untreated and digitonin-treated microsomal fractions was highest at the maximum distribution of plasma membranes.

scholarly journals The dream team meets liver perfusion: From gluconeogenesis to hepatic physiology

2012 ◽  
Vol 34 (1) ◽  
pp. 35-37
Author(s):  
John T. Brosnan ◽  
Margaret E. Brosnan
Keyword(s):  
Rat Liver ◽  
Liver Perfusion ◽  
Biochemical Journal ◽  
Liver Preparation ◽  
Classic Paper

This Biochemical Journal ‘Classic Paper’ article describes the development in the Krebs laboratory of a simple and robust procedure for perfusion of the rat liver. Although initially designed for the study of gluconeogenesis, the procedure has been widely used for a variety of studies which require a physiological in vitro liver preparation.

Utilization of fatty acids by rat liver slices as a function of medium concentration

1964 ◽  
Vol 206 (2) ◽  
pp. 345-350 ◽  
Author(s):  
Herbert Rose ◽  
Martha Vaughan ◽  
Daniel Steinberg
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Rat Liver ◽  
Neutral Lipids ◽  
Specific Radioactivity ◽  
Lipid Synthesis ◽  
Normal Liver ◽  
Precursor Pool ◽  
Liver Slices

The rate of incorporation of palmitate-1-C14 into neutral lipids and phospholipids of rat liver slices in vitro and its conversion to C14O2 were shown to increase markedly as the free fatty acid (FFA) concentration of the medium was increased. Incorporation into lipids and conversion to C14O2 proceeded linearly with time over 60 min. The incorporation of glycerol-1,3-C14 into neutral lipids also increased as the FFA concentration of the medium was increased but incorporation into phospholipids was unchanged. It is concluded that high FFA concentrations cause a true increase in rate of neutral lipid synthesis by liver slices. The associated increase in incorporation of labeled palmitate into phospholipids most likely reflects the higher specific radioactivity of the precursor pool of FFA and/or an exchange reaction rather than a true increase in net synthesis. A method for recovering tissue FFA quantitatively is described. Normal liver was found to contain 0.40–0.87 µEq FFA/g wet wt. The composition of this tissue FFA fraction is presented.

Thyroxine transport from blood to brain via transthyretin synthesis in choroid plexus

1990 ◽  
Vol 258 (2) ◽  
pp. R338-R345 ◽  
Author(s):  
G. Schreiber ◽  
A. R. Aldred ◽  
A. Jaworowski ◽  
C. Nilsson ◽  
M. G. Achen ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Thyroid Hormones ◽  
Choroid Plexus ◽  
Intravenous Injection ◽  
Rat Liver ◽  
Specific Radioactivity ◽  
Perfusion Medium ◽  
The Brain

The transport of thyroxine from the bloodstream to the brain and the synthesis and secretion of transthyretin (formerly called prealbumin) were studied in rats and in sheep choroid plexus perfused in vitro. Rat choroid plexus contained 4.4 micrograms and rat liver 0.39 micrograms transthyretin mRNA per gram wet tissue. The specific radioactivity of transthyretin isolated from cerebrospinal fluid of rats 60 min after intravenous injection of [14C]leucine was greater than 50 times that of transthyretin from serum. After adding [14C]leucine to the perfusion medium of an in vitro perfused sheep choroid plexus, highly radioactive transthyretin was isolated from freshly secreted cerebrospinal fluid collected from the exposed choroid plexus surface. Secretion of newly synthesized transthyretin into the perfusion medium could not be demonstrated. After intravenous injection of [125I]-thyroxine into rats, a maximum in the curve of radioactivity in tissue plotted against time after injection was observed first for choroid plexus, thereafter for cerebrospinal fluid, and still later for cortex and striatum. Based on the obtained data, a hypothesis is derived for the mechanism of the transport of thyroid hormones from the bloodstream to the brain involving transthyretin synthesized in choroid plexus and secreted into the cerebrospinal fluid.

scholarly journals The synthesis of bile acids in perfused rat liver subjected to chronic biliary drainage

1970 ◽  
Vol 118 (3) ◽  
pp. 519-530 ◽  
Author(s):  
I. W. Percy-Robb ◽  
G. S. Boyd
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Cholic Acid ◽  
Rat Liver ◽  
Chenodeoxycholic Acid ◽  
Biliary Drainage ◽  
Specific Radioactivity ◽  
Mevalonic Acid ◽  
Liver Cholesterol ◽  
Microscopic Appearance

1. Isolated rat liver was perfused with heparinized whole blood under physiological pressure resulting in the secretion of bile at about the rate observed in vivo. 2. The preparation remained metabolically active for 4h and was apparently normal in function and microscopic appearance. 3. When the perfusate plasma and liver cholesterol pool was labelled by the introduction of [2-14C]mevalonic acid the specific radioactivity of the perfusate cholesterol increased. The biliary acids (cholic acid and chenodeoxycholic acid) were labelled and had the same specific radioactivity. 4. Livers removed from rats immediately after, and 40h after, the start of total biliary drainage, were perfused; increased excretion rates of both cholic acid and chenodeoxycholic acid were found when the liver donors had been subjected to biliary drainage. 5. The incorporation of [2-14C]mevalonic acid or rat lipoprotein labelled with [14C]cholesterol into bile acids was studied. 6. A dissociation between the mass of bile acid excreted and the rate of incorporation of 14C was found. This was attributed to the changing specific radioactivity of the cholesterol pool acting as the immediate bile acid precursor.

Assessment of Gall-Bladder Storage Function in Man

1983 ◽  
Vol 65 (2) ◽  
pp. 185-191 ◽  
Author(s):  
R. P. Jazrawi ◽  
R. M. Kupfer ◽  
C. Bridges ◽  
A. Joseph ◽  
T. C. Northfield
Keyword(s):  
Bile Acid ◽  
Gall Bladder ◽  
Bile Acids ◽  
Saturation Index ◽  
Biliary Lipid ◽  
Fasting State ◽  
Bile Acid Pool ◽  
Acid Pool ◽  
Lipid Mass

1. We have validated a scintiscanning method for measuring fasting-state gall-bladder (GB) filling in man. 99mTc-labelled diethyl phenylcarbamoylmethyliminodiacetate (Tc-HIDA) was given intravenously, and 90 min later GB and gut activity were measured by using two isosensitive rectilinear scanning heads (anterior and posterior). Studies with a phantom GB in vitro, and studies in man in vivo, showed that the maximum error due to differences in isotope depth was 8%, compared with 300% when only one head was used. 2. By combining this technique with measurement of biliary lipid concentrations of fasting-state GB bile obtained by nasoduodenal intubation and intravenous cholecystokinin infusion, we were able to measure for the first time the total mass of all three biliary lipids in the GB. GB bile samples obtained in this way were divided into three consecutive portions of equal size in order to assess GB mixing. Bile acid pool size was also measured by isotope dilution. 3. We studied 12 healthy non-obese men. Fasting-state GB filling over 90 min (mean ± sem) was 54 ±8%. Biliary lipid mass in GB was 4.9 ±0.5 mmol for bile acids (67 ± 5% of the total bile acid pool), 1.6 ±0.2 mmol for phospholipid and 0.5 ± 0.1 mmol for cholesterol. The three consecutive portions of fasting GB bile gave values of 1.05 ± 0.07, 1.05 ± 0.06 and 1.03 ±0.10 for cholesterol saturation index (SI) and 6.6 ±1.1, 7.4 ± 1.6 and 6.5 ± 1.0 for Tc-HIDA c.p.m. × 1000 per mmol of bile acids. 4. The SI of fasting-state GB bile was significantly correlated with fasting-state GB filling (r = 0.63; P < 0.05). It was also correlated with cholesterol mass in GB (r = 0.64; P < 0.05), but not with bile acid and phospholipid mass. 5. We conclude that: (a) valid measurements of GB filling can be made in man by a simple scintiscanning technique employing 99mTc-HIDA as a biliary marker; (b) biliary lipid mass can also be measured if GB bile is obtained; (c) SI in health is in part determined by the degree of fasting-state GB filling, and in part by cholesterol mass in GB; (d) fasting-state GB content is well mixed in health.

scholarly journals Chenodeoxycholate Is a Potent Inducer of the Permeability Transition Pore in Rat Liver Mitochondria

2001 ◽  
Vol 21 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Anabela P. Rolo ◽  
Paulo J. Oliveira ◽  
António J. M. Moreno ◽  
Carlos M. Palmeira
Keyword(s):  
Bile Acids ◽  
Rat Liver ◽  
Cell Injury ◽  
Disease Process ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Potent Inducer

Several reports support the concept that bile acids may be cytotoxic during cholestatic disease process by causing mitochondrial dysfunction. Here we report additional data and findings aimed at a better understanding of the involvement of the permeability transition pore (PTP) opening in bile acids toxicity. The mitochondrial PTP is implicated as a mediator of cell injury and death in many situations. In the presence of calcium and phosphate, chenodeoxycholic acid (CDCA) induced a permeability transition in freshly isolated rat liver mitochondria, characterized by membrane depolarization, release of matrix calcium, and osmotic swelling. All these events were blocked by cyclosporine A (CyA) and the calcium uniporter inhibitor ruthenium red (RR). The results suggest that CDCA increases the sensitivity of isolated mitochondria in vitro to the calcium-dependent induction of the PTP.

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