scholarly journals Hydroperoxide-induced chemiluminescence of the perfused lung

1980 ◽  
Vol 192 (1) ◽  
pp. 303-309 ◽  
Author(s):  
E Cadenas ◽  
I D Arad ◽  
A B Fisher ◽  
A Boveris ◽  
B Chance
Keyword(s):  
Microsomal Fraction ◽  
Light Emission ◽  
Time Dependent ◽  
Butyl Hydroperoxide ◽  
Time Dependent Process ◽  
Perfused Lung ◽  
Liver Microsomal Fraction ◽  
Alveolar Oedema ◽  
Hydroperoxide Concentration

Light-emission of the perfused lung is induced by t-butyl hydroperoxide, giving chemiluminescence yields that oscillate between 800 and 1500 counts/s depending on the site and position of the lung. The response of the perfused lung to infusion with different hydroperoxides gives a pattern similar to that observed with the liver microsomal fraction; ethyl hydroperoxide shows a much higher chemiluminescence yield than the tertiary (t-butyl and cumene)hydroperoxides. Alveolar oedema affected the light-emission of the perfused lung depending on the time at which oedema developed, decreasing light emission on infusion of hydroperoxide in the oedematous lung and increasing it when oedema appeared after the maximal chemiluminescence yield was already achieved. Paraquat, administered in vivo, augmented light-emission by approximately 2-fold. The effect of paraquat was a time-dependent process. Lung chemiluminescence, compared with liver chemiluminescence, needed higher hydroperoxide concentration to induce light-emission.

Mitochondrial Biotransformation of Drugs and Other Xenobiotics

2021 ◽  
Vol 22 ◽  
Author(s):  
Hilmi Orhan ◽  
Fuat Karakuş ◽  
Ali Ergüç
Keyword(s):  
Microsomal Fraction ◽  
Lipid Lowering ◽  
Metabolizing Enzymes ◽  
Xenobiotic Metabolizing Enzymes ◽  
Two Factors ◽  
Liver Microsomal Fraction ◽  
The Origin Of Life ◽  
Major Factors

: In vivo biotransformation of exposed chemicals is one of the major factors that determine the concentration and the duration of a substance at the systemic site of effect. Given that toxicity is expressed as a function of two factors, namely dose and time, the type and intensity of the toxicity are directly dependent on the chemical transformation of the exposed parent substance. This dependency involves two different situations. The amount of the chemical reaching the target will be decreased with the extent of metabolism if the parent chemical is toxic. The opposite is true if the metabolite(s) is toxic instead. To date, the liver microsomal fraction in mammals has been justifiably considered the centre of biotransformation reactions as the liver and microsomes (i.e., endoplasmic reticulum component of the cell) possess the most abundant types and quantities of xenobiotic-metabolizing enzymes, especially the cytochrome P450 supergene enzyme family. These enzymes are common in all kingdoms of life, which strongly suggests that the origin of life is common. It is already known that various drugs enter mitochondria by different mechanisms, and this translocation is believed to be responsible for mitochondrial effects that are part of the therapeutic actions of various drugs such as lipid-lowering statins or antidiabetogenic thiazolidindiones. However, the discovery of mitochondrial forms of the xenobiotic-metabolizing enzymes provoked discussions about whether mitochondria metabolize drugs and other chemicals to some extent. This possibility may particularly be important as mitochondria have various critical cellular structures and functions. In the case of in situ generated metabolite(s), when there are adverse interactions with either these structures or functions, various toxic outcomes may appear. In this review, we compiled studies in the literature regarding biotransformation of drugs and other chemicals catalysed by mitochondria, where it is both an initiator and target of toxicity.

scholarly journals The apparent absence of involvement of biotin in the vitamin K-dependent carboxylation of glutamic acid residues of proteins

1977 ◽  
Vol 163 (1) ◽  
pp. 39-43 ◽  
Author(s):  
P A Friedman ◽  
M A Shia
Keyword(s):  
Glutamic Acid ◽  
Vitamin K ◽  
Microsomal Fraction ◽  
Male Rats ◽  
Biotin Deficiency ◽  
Deficient Diet ◽  
Carboxylase Activity ◽  
Liver Microsomal Fraction

The mechanism of the vitamin K-dependent post-translational carboxylation of the gamma-carbon atom of glutamic acid residues in proteins remains obscure. Experiments were performed in vivo and in vitro in an attempt to establish a role for biotin in the transfer of the carboxyl group. Weanling male rats were fed on a biotin-deficient diet until severe biotin deficiency was induced. Their degree of biotin deficiency was documented by assaying for liver acetyl-CoA carboxylase activity, which was about 15% of normal. However, one-stage and two-stage prothrombin times measured on the plasmas were normal. In addition, the liver microsomal fraction did not contain any more prothrombin precursor than did that of normal rat liver. Experiments were done in vitro in which vitamin K-dependent fixing of 14CO2 was measured in the liver microsomal fraction from vitamin K-deficient male rats in the presence or absence of avidin. No evidence for an avidin-sensitive critical biotin-containing site was obtained. Thus neither series of experiments suggests a role for biotin; the data are compatible with carboxyl transfer occurring either through a carboxylated vitamin K intermediate; or via a yet to be identified intermediate, or perhaps via CO2 itself.

scholarly journals Conditions that may result in (de-)phosphorylation of hepatic acyl-CoA:cholesterol acyltransferase result also in modulation of substrate supply in vitro

1984 ◽  
Vol 221 (3) ◽  
pp. 685-695 ◽  
Author(s):  
K A Mitropoulos ◽  
S Venkatesan
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Covalent Modification ◽  
Time Dependent ◽  
Cholesterol Concentration ◽  
Acat Activity ◽  
Phospholipid Liposomes ◽  
Substrate Supply ◽  
Rate Of Increase ◽  
Liver Microsomal Fraction

The present experiments were designed to study intervesicular transfer of cholesterol in rat liver microsomal fraction and modulation of the activity of acyl-CoA:cholesterol acyltransferase (ACAT) under conditions that are expected to result in the covalent modification (phosphorylation/dephosphorylation) of the enzyme. Preincubation of rat liver microsomal fraction followed by assay of ACAT showed a time-dependent increase in activity. This rate was temperature-dependent. Preincubation in the presence of cholesterol/phospholipid liposomes resulted in a time-dependent transfer of cholesterol from liposomal to the microsomal vesicles and in an increase in the rate of ACAT change owing to the preincubation. Both these rates were dependent on liposomal cholesterol concentration and on temperature. The presence of cytosol in the preincubation mixture increased the rate of change of ACAT activity in the absence or in the presence of cholesterol/phospholipid liposomes. In the latter case the presence of cytosol also increased the rate of transfer of cholesterol from liposomal to the microsomal vesicles. Activation energies of the rate of this transfer and of the rate of increase of ACAT activity were similar in the presence and in the absence of cytosol. Both in the absence and in the presence of cytosol, the presence of NaF (50 mM) in the preincubation mixture considerably decreased the rate of transfer of cholesterol from liposomal to microsomal vesicles and the rate of increase of ACAT activity. The presence of Mg2+ in the preincubation mixture produced no effect on the rate of transfer of cholesterol from liposomal to the microsomal vesicles, although under most conditions it decreased the rate of increase of ACAT activity caused by the preincubation. These results are discussed in relation to the molecular mechanism involved in this intervesicular transfer of cholesterol and to the modulation of ACAT activity by substrate supply, and also in relation to the hypothesis that ACAT activity can be modulated by a mechanism involving the phosphorylation/dephosphorylation of the enzyme.

scholarly journals Binding of trichloromethyl radicals to lipids of the hepatic endoplasmic reticulum during tetrachloromethane metabolism

1984 ◽  
Vol 223 (3) ◽  
pp. 577-586 ◽  
Author(s):  
B Link ◽  
H Dürk ◽  
D Thiel ◽  
H Frank
Keyword(s):  
Fatty Acids ◽  
Microsomal Fraction ◽  
Covalent Binding ◽  
Chemical Structures ◽  
Different Types ◽  
Liver Microsomal Fraction ◽  
Liquid Chromatographic ◽  
Trichloromethyl Radical

Metabolism of tetrachloromethane (carbon tetrachloride) by liver microsomal fraction under anaerobic conditions and in vivo leads to covalent binding of trichloromethyl radicals to lipids. The resulting covalently modified lipids contain two different types of fatty acids: a group of monomeric trichloromethyl fatty acid residues, usually with one double bond less than the precursor fatty acids, and a group of fatty acids that are not sufficiently volatile for gas chromatography. The liquid-chromatographic properties of the latter indicate high molecular mass, presumably due to cross-linking. The chemical structures of the monomeric fatty acids were elucidated, and these support the view that the most significant reactive metabolite of tetrachloromethane is the trichloromethyl radical. The isomer patterns of the monomeric trichloromethyl fatty acids in vitro and in vivo are almost identical, which shows that anaerobic incubation of tetrachloromethane with microsomal fraction very well reflects the processes involved in hepatotoxicity of tetrachloromethane in vivo.

scholarly journals On the mechanism of the modulation in vitro of acyl-CoA:cholesterol acyltransferase by progesterone

1983 ◽  
Vol 215 (1) ◽  
pp. 191-199 ◽  
Author(s):  
S Synouri-Vrettakou ◽  
K A Mitropoulos
Keyword(s):  
Microsomal Fraction ◽  
Rate Of Change ◽  
Time Dependent ◽  
Cholesterol Concentration ◽  
Phosphatidylcholine Liposomes ◽  
Acat Activity ◽  
Rate Of Increase ◽  
A Site

The assay of acyl-CoA:cholesterol acyltransferase (ACAT) in the presence of progesterone resulted in a lower enzyme activity and this inhibition was dependent on the concentration of steroid in the assay mixture. The incubation at 37 degrees C of rat liver microsomal fraction followed by the re-isolation of treated microsomal vesicles and the assay of ACAT resulted in a pre-incubation-time-dependent increase in the activity of the enzyme. This rate of increase was inhibited by the presence of progesterone in the pre-incubation mixture. The incubation of the microsomal fraction in the presence of cholesterol/phosphatidylcholine liposomes, followed by the re-isolation of the treated microsomal vesicles and assay of ACAT, resulted in time-dependent and liposomal cholesterol-concentration-dependent transfer of cholesterol to microsomal vesicles and in an increase in the activity of ACAT. The presence of progesterone during pre-incubation had no effect on the rate of transfer of liposomal cholesterol to the microsomal vesicles. However, progesterone decreased the rate of change in ACAT activity. This effect can be attributed to progesterone associated with treated microsomal vesicles and present during the enzyme assay. Consistent with this, the presence of progesterone has no effect on the size of the non-esterified cholesterol pool that acts as substrate for ACAT. The size of the ACAT substrate pool was modulated in vitro or in vivo and ACAT activity was assayed in the presence of various concentrations of progesterone. The data suggest that the interaction of the steroid with ACAT is at a site other than the catalytic site and that changes in the size of the substrate pool are associated with an increase in ACAT activity, but do not result in changes in the conformation of the enzyme or in co-operative transitions of the enzyme.

The Natural Flavonoid Naringenin Inhibits the Cell Growth of WilmsTumorinChildren by Suppressing TLR4/NF-κB Signaling

2020 ◽  
Vol 20 ◽  
Author(s):  
Hongtao Li ◽  
Peng Chen ◽  
Lei Chen ◽  
Xinning Wang
Keyword(s):  
Cell Growth ◽  
Western Blot ◽  
Wilms Tumor ◽  
Critical Role ◽  
Time Dependent ◽  
Luciferase Assay ◽  
Dependent Manner ◽  
Tlr4 Expression ◽  
Protein Levels

Background: Nuclear factor kappa B (NF-κB) is usually activated in Wilms tumor (WT) cells and plays a critical role in WT development. Objective: The study purpose was to screen a NF-κB inhibitor from natural product library and explore its effects on WT development. Methods: Luciferase assay was employed to assess the effects of natural chemical son NF-κB activity. CCK-8 assay was conducted to assess cell growth in response to naringenin. WT xenograft model was established to analyze the effect of naringenin in vivo. Quantitative real-time PCR and Western blot were performed to examine the mRNA and protein levels of relative genes, respectively. Results: Naringenin displayed significant inhibitory effect on NF-κB activation in SK-NEP-1 cells. In SK-NEP-1 and G-401 cells, naringenin inhibited p65 phosphorylation. Moreover, naringenin suppressed TNF-α-induced p65 phosphorylation in WT cells. Naringenin inhibited TLR4 expression at both mRNA and protein levels in WT cells. CCK-8 staining showed that naringenin inhibited cell growth of the two above WT cells in dose-and time-dependent manner, whereas Toll-like receptor 4 (TLR4) over expression partially reversed the above phenomena. Besides, naringenin suppressed WT tumor growth in dose-and time-dependent manner in vivo. Western blot found that naringenin inhibited TLR4 expression and p65 phosphorylation in WT xenograft tumors. Conclusion: Naringenin inhibits WT development viasuppressing TLR4/NF-κB signaling

Influence of 1,4-benzdiazepin-2-ones on rat liver microsomal fraction and hepatocytes

1987 ◽  
Vol 21 (1) ◽  
pp. 5-8
Author(s):  
T. I. Davidenko ◽  
O. V. Sevast'yanov ◽  
L. N. Yakubovskaya
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Liver Microsomal Fraction

scholarly journals In vivo analysis of the size- and time-dependent uptake of NaYF4:Yb,Er upconversion nanocrystals by pumpkin seedlings

2015 ◽  
Vol 3 (1) ◽  
pp. 144-150 ◽  
Author(s):  
J. Nordmann ◽  
S. Buczka ◽  
B. Voss ◽  
M. Haase ◽  
K. Mummenhoff
Keyword(s):  
Time Dependent ◽  
Upconversion Nanocrystals ◽  
In Vivo Analysis ◽  
Kinetics Of

We have investigated the kinetics of the uptake and the translocation of nanoparticles of different size in plants.

scholarly journals Loss of haem in rat liver caused by the porphyrogenic agent 2-allyl-2-isopropylacetamide

1971 ◽  
Vol 124 (4) ◽  
pp. 767-777 ◽  
Author(s):  
F. De Matteis
Keyword(s):  
Rat Liver ◽  
Microsomal Fraction ◽  
Direct Evidence ◽  
Gradual Increase ◽  
Rapid Loss ◽  
Metabolizing Enzymes ◽  
Liver Microsomal Fraction ◽  
Green Pigments ◽  
Cytochrome P 450 ◽  
Increased Activity

1. The effect of a single dose of 2-allyl-2-isopropylacetamide on the cytochrome P-450 concentration in rat liver microsomal fraction was studied. The drug caused a rapid loss of cytochrome P-450 followed by a gradual increase to above the normal concentration. 2. The loss of cytochrome P-450 was accompanied by a loss of microsomal haem and by a brown–green discoloration of the microsomal fraction suggesting that a change in the chemical constitution of the lost haem had taken place. Direct evidence for this was obtained by prelabelling the liver haems with radioactive 5-aminolaevulate: the drug caused a loss of radioactivity from the haem with an increase of radioactivity in a fraction containing certain un-identified green pigments. 3. Evidence was obtained by a dual-isotopic procedure that rapidly turning-over haem(s) may be preferentially affected. 4. The loss of cytochrome P-450 as well as the loss of microsomal haem and the discoloration of the microsomal fraction were more intense in animals pretreated with phenobarbitone and were much less evident when compound SKF 525-A (2-diethylaminoethyl 3,3-diphenylpropylacetate) was given before 2-allyl-2-isopropylacetamide, suggesting that the activity of the drug-metabolizing enzymes may be involved in these effects. 5. The relevance of the destruction of liver haem to the increased activity of 5-aminolaevulate synthetase caused by 2-allyl-2-isopropylacetamide is discussed.

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