Interrelationships in the Metabolism of Liver Arachidonoyllecithins and Plasma Cholesteryl Arachidonate in the Rat

1971 ◽  
Vol 49 (9) ◽  
pp. 1005-1011 ◽  
Author(s):  
B. J. Holub ◽  
A. Kuksis
Keyword(s):  
Arachidonic Acid ◽  
Rat Liver ◽  
Molecular Species ◽  
Free Cholesterol ◽  
Plasma Lipids ◽  
Male Rats ◽  
Gradual Release ◽  
Acid Esters ◽  
Net Transfer

Male rats were injected intravenously with albumin-bound 1-14C-arachidonic acid or 1-14C-palmitoyllysolecithin and the molecular species of the labeled liver and plasma lipids were identified after various periods of time. There was an extensive esterification of lysolecithin with arachidonic acid in the rat liver, which was in agreement with the earlier demonstrated specific incorporation of labeled arachidonic acid into the liver lysolecithins. The subsequent gradual release of the labeled liver arachidonoyllecithins into the plasma was accompanied by a steady rise in the radioactivity of plasma cholesteryl arachidonate. In other experiments, it was shown that radioactive arachidonic acid esters of cholesterol are readily formed in vitro from 1-14C-arachidonoyllecithin and free cholesterol, and that such esters upon subsequent injection can contribute arachidonic acid for the biogenesis of lecithin from lysolecithin in the liver as a result of hydrolysis. These results are compatible with the operation of a plasma–liver cycle which results in a net transfer of cholesterol from plasma to the liver and a return of lysolecithin and arachidonic acid to the plasma in the form of lecithin.

THE ROLE OF THE ADRENAL GLAND IN THE CONTROL OF AMINO ACID INCORPORATION INTO PROTEIN OF ISOLATED RAT LIVER MICROSOMES

1960 ◽  
Vol 21 (2) ◽  
pp. 177-189 ◽  
Author(s):  
A. KORNER
Keyword(s):  
Amino Acid ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Female Rats ◽  
Male Rats ◽  
Rat Liver Microsomes ◽  
Hypophysectomized Rats ◽  
Normal Rat ◽  
Secondary Result

SUMMARY 1. Microsomes, isolated from rat liver a day after adrenalectomy, incorporate more radioactive amino acid into their protein in vitro than microsomes from normal rat liver. This enhanced rate of incorporation progressively declines with time after adrenalectomy until it reaches a plateau level which is below the normal rate of incorporation. 2. Following adrenalectomy microsomes isolated from liver of male rats show a greater rise in incorporating ability than those from liver of female rats, and maintain it longer. 3. Most of the increased incorporation observed in the in vitro system soon after adrenalectomy of the rat, and most of the decreased incorporation observed in rats adrenalectomized for some time, results from alterations in the microsomes which change their ability to incorporate activated amino acids into proteins. 4. Treatment of rats with cortisol acetate results in an increase in the ability of liver microsomes to incorporate amino acid into protein. This heightened incorporating ability is probably a secondary result of the breakdown of extrahepatic tissue protein which is stimulated by cortisol. 5. Somewhat similar responses to acute adrenalectomy and to treatment with cortisol were found in hypophysectomized rats. 6. The protein anabolic response of adrenalectomized rats to treatment with insulin, and of adrenalectomized-hypophysectomized rats to treatment with insulin or growth hormone, is greater than that shown by rats which possess adrenal glands.

scholarly journals The effect of phenobarbital on the submicrosomal distribution of uridine diphosphate glucuronyltransferase from rat liver

1970 ◽  
Vol 117 (2) ◽  
pp. 319-324 ◽  
Author(s):  
G. J. Mulder
Keyword(s):  
Enzyme Activity ◽  
Density Gradient ◽  
Rat Liver ◽  
Microsomal Fraction ◽  
Specific Activity ◽  
Sucrose Density Gradient ◽  
Male Rats ◽  
Uridine Diphosphate ◽  
Triton X

1. The detergent Triton X-100 activates UDP glucuronyltransferase from rat liver in vitro six- to seven-fold with p-nitrophenol as substrate. The enzyme activity when measured in the presence of Triton X-100 is increased significantly by pretreatment of male rats with phenobarbital for 4 days (90mg/kg each day intraperitoneally). If no Triton X-100 is applied in vitro such an increase could not be shown. In all further experiments the enzyme activity was measured after activation by Triton X-100. 2. The Km of the enzyme for the substrate p-nitrophenol does not change on phenobarbital pretreatment. 3. When the microsomal fraction from the liver of untreated rats is subfractionated on a sucrose density gradient, 47% of the enzyme activity is recovered in the rough-surfaced microsomal fraction, which also has a higher specific activity than the smooth-surfaced fraction. 4. Of the increase in activity after the phenobarbital pretreatment 50% occurs in the smooth-surfaced fraction, 19% in the rough-surfaced fraction and 31% in the fraction located between the smooth- and rough-surfaced microsomal fractions on the sucrose density gradient. 5. The latency of the enzyme in vitro, as shown by the effect of the detergent Triton X-100, is discussed in relation to the proposed heterogeneity of UDP glucuronyltransferase.

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.

scholarly journals pH-dependency of iodothyronine metabolism in isolated perfused rat liver

1982 ◽  
Vol 202 (3) ◽  
pp. 667-675 ◽  
Author(s):  
J Köhrle ◽  
M J Müller ◽  
R Ködding ◽  
H J Seitz ◽  
R D Hesch
Keyword(s):  
Intracellular Ph ◽  
Rat Liver ◽  
Synthetic Medium ◽  
Weak Acid ◽  
Male Rats ◽  
Isolated Perfused Rat Liver ◽  
Ph Optimum ◽  
Blood Constituents ◽  
Deiodinase Activity

1. Isolated livers from fed male rats were perfused for 2 h with T4 (L-thyroxine), T3 (L-3,3′,5-tri-iodothyronine) or rT3 (L-3,3′,5′-tri-iodothyronine) at different pH values (7.1-7.6) in a fully synthetic medium, whereby normal metabolic functions were maintained without addition of rat blood constituents or albumin. 2. T3 output into the medium and net T3 production reached a maximum at a pH of the medium of 7.2 and significantly decreased with alteration of the pH when livers were perfused with T4 as a substrate. 3. However, the net T4 and T3 uptake by the liver, as well as the hepatic T4 and T3 content after perfusion, were not dependent on the pH of the perfusion when livers were offered T4 or T3 as substrates respectively. 4. Determination of intracellular pH by the analysis of the distribution of the weak acid dimethyloxazolidinedione allows the conclusion that the pH optimum of iodothyronine 5′-deiodinase in the intact perfused liver corresponds to the maximum determined in vitro for the membrane-bound enzyme localized in the endoplasmic reticulum. 5. The rapid 5′-deiodination of rT3 to 3,3′-T2 (L-3,3′-di-iodothyronine), the fast disappearance of 3,3′-T2, and the fact that no net rT3 production from T4 could be detected, supports the hypothesis that in rat liver iodothyronine 5′-deiodinase activity seems to predominate over iodothyronine 5-deiodinase activity. 6. Thus the rat liver can be considered in normal physiological situations as an organ forming T3 from T4 and deiodinating rT3 originating from extrahepatic tissues, whereby the cellular iodothyronine 5′-deiodination rate is controlled by the intracellular pH.

scholarly journals A fraction derived from brewer's yeast inhibits cholesterol synthesis by rat liver preparations in vitro

1991 ◽  
Vol 65 (2) ◽  
pp. 285-299 ◽  
Author(s):  
E. S. Holdsworth ◽  
D. V. Kaufman ◽  
E. Neville
Keyword(s):  
Rat Liver ◽  
Plasma Lipids ◽  
Normal Diet ◽  
Water Soluble ◽  
Sterol Synthesis ◽  
Brewer’S Yeast ◽  
Nicotinamide Riboside ◽  
Brewer's Yeast

Brewer's yeast was grown on a defined medium containing tracer51Cr with or without added chromium. The two batches of yeast contained 10 μg/g (high-Cr) or 80 ng/g (low-Cr). Extracts were prepared and fractionated. A third batch of yeast (third batch) was grown with added Cr, and fractionated. Rats were reared on either rat cubes (normal diet) or on a low-Cr diet (low-Cr), or on rat cubes with added cholestyramine (cholestyramine diet). Preparations of rat liver, both cell-free and intact hepatocytes, incorporated acetate-carbon into fatty acids and cholesterol. These processes were inhibited by a yeast fraction containing small, neutral, water-soluble compounds. The degree of inhibition was the same whether the liver came from normal rats or rats fed on the low-Cr diet. Similarly the inhibitory effect was found with identical amounts of extracts from low- or high-Cr yeasts. Therefore, Cr compounds do not appear to account for the inhibitory effects of brewer's yeast. Use of other substrates indicated that the site of inhibition of sterol synthesis was apparently between acetyl-CoA and mevalonate. One inhibitory substance was isolated from yeast and was found to be nicotinamide riboside. This may have been produced from NAD(P) during the preparation of yeast extracts, and it may be produced from dietary yeast supplements during digestion in vivo. Nicotinamide riboside may be partly responsible for the reported effects of yeast supplements on plasma lipids in humans.

scholarly journals Effect of dietary fats on the δ6- and δ5-desaturation of fatty acids in rat liver microsomes

1983 ◽  
Vol 50 (3) ◽  
pp. 749-756 ◽  
Author(s):  
D. Kirstein ◽  
C.-E. Høy ◽  
G. Hølmer
Keyword(s):  
Arachidonic Acid ◽  
Linolenic Acid ◽  
Rat Liver ◽  
Desaturase Activity ◽  
Liver Microsomes ◽  
Dietary Fats ◽  
Rat Liver Microsomes ◽  
Δ5 Desaturase ◽  
Substrate Level

1. Rats were given diets containing (% dietary energy): 46 arachis oil (AO), 36 partially-hydrogenated arachis oil (HAO) + 10 AO, 36 partially-hydrogenated marine oil (HMO) + 10 AO, or 46 of a combination of rape-seed oils high and low in erucic acid (RSO + LERSO).2. In the liver microsomes the content of arachidonic acid (20:4ω6) was reduced inthe groups given HAO + AO and HMO + AO.3. The rates of Δ6-desaturation of linoleic acid into γ-linolenic acid (18:3ω6) and of Δ5-desaturation of dihomo-γ-linolenic acid into arachidonic acid were studied in vitro at two substrate levels: a high substrate level reflecting maximal microsomal desaturase activity in rat liver and a low substrate level reflecting desaturase activity under physiological conditions.4. Dietary HAO, rich in 18:1 isomers, suppressed the Δ6-desaturase activity butnot the Δ5-desaturase activity. Dietary HMO, rich in 18:1, 20:1 and 22:1 isomers, reduced both Δ6- and Δ5-desaturase activities.

scholarly journals The Effect of (-)-Linalool on the Metabolic Activity of Liver CYP Enzymes in Rats

2016 ◽  
pp. S499-S504 ◽  
Author(s):  
K. NOSKOVÁ ◽  
G. DOVRTĚLOVÁ ◽  
O. ZENDULKA ◽  
R. ŘEMÍNEK ◽  
J. JUŘICA
Keyword(s):  
Rat Liver ◽  
Metabolic Activity ◽  
Systemic Treatment ◽  
Competitive Inhibition ◽  
Floral Scent ◽  
Liver Microsomes ◽  
Inhibitory Effect ◽  
Male Rats ◽  
Rat Liver Microsomes

(-)-Linalool is the major floral scent occurring mainly in families Lamiaceae, Lauraceae and Rutaceae and is the main active compound of lavender oil. The purpose of this study was to reveal the influence of subchronic systemic treatment with (-)-linalool on the metabolic activity of CYP2A, 2B, 2C6, 2C11 and 3A in rat liver microsomes (RLM). The second aim was to reveal possible inhibitory effect of (-)-linalool on CYP2C6 in vitro. Wistar albino male rats were treated with (-)-linalool intragastrically at the doses of 40, 120, and 360 mg/kg/day for 13 days. Treatment with (-)-linalool at the dose of 360 mg/kg increased the metabolic activity of CYP2A assessed with testosterone as a probe substrate. (-)-Linalool showed weak competitive inhibition of CYP2C6 in rat liver microsomes, with IC50 of 84 μM with use of diclofenac as a probe substrate.

Glucocorticoid and estrogen regulation of corticosteroid-binding globulin production by rat liver.

1979 ◽  
Vol 237 (6) ◽  
pp. E493 ◽  
Author(s):  
D Feldman ◽  
C E Mondon ◽  
J A Horner ◽  
J N Weiser
Keyword(s):  
Rat Liver ◽  
Binding Sites ◽  
Hormonal Regulation ◽  
Liver Slice ◽  
Male Rats ◽  
Perfused Liver ◽  
Production Rates ◽  
Estrogen Regulation ◽  
Corticosteroid Binding Globulin

We have recently demonstrated that rat liver can synthesize and secrete corticosteroid-binding globulin (CBG). The present study extends these observations and examines the hormonal regulation of hepatic CBG production. Male rats were pretreated by adrenalectomy and/or glucocorticoid or estrogen administration and the rate of CBG production was measured in vitro. The production rates were assessed by the generation of specific corticosterone binding sites in both a liver-slice preparation and in an isolated perfused liver. The two techniques showed qualitatively similar results. Adrenalectomy enhanced and glucorticoid administration inhibited the rate of CBG production and secretion. Pretreatment of male rats with estradiol stimulated the rate of CBG production. The production rates were 20- to 40-fold higher in the perfused liver demonstrating its superiority over the liver-slice system. The livers from intact rats secreted CBG binding sites at a rate of approximately 18 pmol/g liver per hours, generating an estimated 20% of the total CBG content of a rat each day. The possible clinical implications of the therapeutic use of glucocorticoids that bind to CBG, yet inhibit CBG production, are discussed.

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