Peroxidase-catalyzed conjugation of [4-14C] estradiol with albumin and thiols

1970 ◽  
Vol 48 (11) ◽  
pp. 1192-1198 ◽  
Author(s):  
P. H. Jellinck ◽  
Rosemarie Fletcher
Keyword(s):  
Horseradish Peroxidase ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Model System ◽  
Water Soluble ◽  
Rat Liver Microsomes ◽  
Two Systems

The mechanism of conjugation of estradiol with either albumin or various thiols in the presence of horseradish peroxidase was studied and these two systems were shown to differ in a number of ways. With albumin, the reaction was slow, required Mn2+, and was inhibited by catalase but not iodoacetamide. In contrast, the reaction with thiols was rapid, did not require Mn2+, and was relatively insensitive to catalase. The yield of conjugates with different thiols and the effect of various inhibitors were also determined. The nature of the water-soluble steroid conjugate was investigated and the product obtained with glutathione shown to differ from that formed by rat liver microsomes. The possible extension of this model system to the situation existing in estrogen-stimulated uteri is discussed.

Oxidation of N-nitrosopiperidine in the udenfriend model system and its metabolism by rat-liver microsomes

1975 ◽  
Vol 24 (5) ◽  
pp. 621-626 ◽  
Author(s):  
Margaret P. Rayman ◽  
Brian C. Challis ◽  
Peter J. Cox ◽  
Michael Jarman
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Model System ◽  
Rat Liver Microsomes

Covalent Binding of Catechol Estrogens to Glutathione Catalyzed by Horseradish Peroxidase, Lactoperoxidase, or Rat Liver Microsomes

1998 ◽  
Vol 11 (8) ◽  
pp. 917-924 ◽  
Author(s):  
Kai Cao ◽  
Prabu D. Devanesan ◽  
Ragulan Ramanathan ◽  
Michael L. Gross ◽  
Eleanor G. Rogan ◽  
...  
Keyword(s):  
Horseradish Peroxidase ◽  
Rat Liver ◽  
Covalent Binding ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Catechol Estrogens

INHIBITION OF14C-ESTRONE METABOLISM IN RAT LIVER MICROSOMES BY 2-HYDROXYESTROGENS AND RELATED COMPOUNDS

1965 ◽  
Vol 43 (2) ◽  
pp. 281-290 ◽  
Author(s):  
Catherine Lazier ◽  
P. H. Jellinck
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Structural Features ◽  
Water Soluble ◽  
Rat Liver Microsomes ◽  
Synthetic Estrogen ◽  
Natural Estrogens ◽  
Water Soluble Protein ◽  
Inhibition Studies ◽  
Related Compounds

Inhibition studies with compounds having structural features in common with the natural estrogens have shown that 2-hydroxyestrone and 2-hydroxyestradiol are potent inhibitors of the rat liver microsomal system, which converts estrone to water-soluble protein-bound products. Simple phenols and naphthols hydroxylated in the ortho and para positions were also found to be good inhibitors, but the corresponding meta-hydroxylated compounds, as well as various anthraquinones and estrogens substituted in the 6, 10, or 16 positions, were inactive in this respect. The synthetic estrogen, hexestrol, lost its inhibitory activity on conversion to dihydroxy hexestrol, a nonestrogenic analogue. The type of inhibition produced by 2-hydroxyestrone, equilenin, diethylstilbestrol, and menadione has been determined by the Lineweaver–Burk method and shown to be competitive for the first three of these compounds.

CHANGES IN OESTROGEN METABOLISM INDUCED IN RAT LIVER MICROSOMES BY SUBCUTANEOUS PELLETS OF OESTRONE AND TESTOSTERONE

1967 ◽  
Vol 39 (1) ◽  
pp. 99-104 ◽  
Author(s):  
P. H. JELLINCK ◽  
JANETTE WOO
Keyword(s):  
Rat Liver ◽  
Specific Activity ◽  
Liver Microsomes ◽  
Hepatic Metabolism ◽  
Water Soluble ◽  
High Yield ◽  
Male Rat ◽  
Rat Liver Microsomes ◽  
Time Intervals ◽  
Rate Of Absorption

SUMMARY Oestrone administered in the form of subcutaneous pellets produced marked changes in the metabolism of [14C]oestradiol by male rat liver microsomes. The high yield of both 2-hydroxyoestradiol and water-soluble metabolites was decreased to the level normally observed in females and this effect was induced by relatively small amounts of oestrogen within a few days after implantation. The action of testosterone on the hepatic metabolism of oestrogens was also investigated together with the effect of removing the hormone pellets at different time intervals. In addition, the rate of absorption of the steroids was determined by direct weighing and, in the case of oestrone, controlled by using radioactive pellets of known specific activity.

scholarly journals Rat liver microsomes catalyse mannosyl transfer from GDP-d-mannose to retinyl phosphate with high efficiency in the absence of detergents

1981 ◽  
Vol 200 (3) ◽  
pp. 529-538 ◽  
Author(s):  
Yoshihiro Shidoji ◽  
Luigi M. De Luca
Keyword(s):  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Rat Liver ◽  
Bovine Serum ◽  
High Efficiency ◽  
Liver Microsomes ◽  
Water Soluble ◽  
Rat Liver Microsomes ◽  
Uptake System ◽  
Dolichyl Phosphate

In the absence of detergent, the transfer of mannose from GDP-mannose to rat liver microsomal vesicles was highly stimulated by exogenous retinyl phosphate in incubations containing bovine serum albumin, as measured in a filter binding assay. Under these conditions 65% of mannose 6-phosphatase activity was latent. The transfer process was linear with time up to 5min and with protein concentration up to 1.5mg/0.2ml. It was also temperature-dependent. The microsomal uptake of mannose was highly dependent on retinyl phosphate and was saturable against increasing amounts of retinyl phosphate, a concentration of 15μm giving half-maximal transfer. The uptake system was also saturated by increasing concentrations of GDP-mannose, with an apparent Km of 18μm. Neither exogenous dolichyl phosphate nor non-phosphorylated retinoids were active in this process in the absence of detergent. Phosphatidylethanolamine and synthetic dipalmitoylglycerophosphocholine were also without activity. Several water-soluble organic phosphates (1.5mm), such as phenyl phosphate, 4-nitrophenyl phosphate, phosphoserine and phosphocholine, did not inhibit the retinyl phosphate-stimulated mannosyl transfer to microsomes. This mannosyl-transfer activity was highest in microsomes and marginal in mitochondria, plasma and nuclear membranes. It was specific for mannose residues from GDP-mannose and did not occur with UDP-[3H]galactose, UDP- or GDP-[14C]glucose, UDP-N-acetyl[14C]-glucosamine and UDP-N-acetyl[14C]galactosamine, all at 24μm. The mannosyl transfer was inhibited 85% by 3mm-EDTA and 93% by 0.8mm-amphomycin. At 2min, 90% of the radioactivity retained on the filter could be extracted with chloroform/methanol (2:1, v/v) and mainly co-migrated with retinyl phosphate mannose by t.l.c. This mannolipid was shown to bind to immunoglobulin G fraction of anti-(vitamin A) serum and was displaced by a large excess of retinoic acid, thus confirming the presence of the β-ionone ring in the mannolipid. The amount of retinyl phosphate mannose formed in the bovine serum albumin/retinyl phosphate incubation is about 100-fold greater than in incubations containing 0.5% Triton X-100. In contrast with the lack of activity as a mannosyl acceptor for exogenous dolichyl phosphate in the present assay system, endogenous dolichyl phosphate clearly functions as an acceptor. Moreover in the same incubations a mannolipid with chromatographic properties of retinyl phosphate mannose was also synthesized from endogenous lipid acceptor. The biosynthesis of this mannolipid (retinyl phosphate mannose) was optimal at MnCl2 concentrations between 5 and 10mm and could not be detected below 0.6mm-MnCl2, when synthesis of dolichyl phosphate mannose from endogenous dolichyl phosphate was about 80% of optimal synthesis. Under optimal conditions (5mm-MnCl2) endogenous retinyl phosphate mannose represented about 20% of dolichyl phosphate mannose at 15min of incubation at 37°C.

scholarly journals Localization and biosynthesis of NADH-cytochrome b5 reductase, an integral membrane protein, in rat liver cells. II. Evidence that a single enzyme accounts for the activity in its various subcellular locations.

1980 ◽  
Vol 85 (3) ◽  
pp. 516-526 ◽  
Author(s):  
J Meldolesi ◽  
G Corte ◽  
G Pietrini ◽  
N Borgese
Keyword(s):  
Cytochrome C ◽  
Rat Liver ◽  
Reductase Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Cytochrome B5 ◽  
Liver Microsomes ◽  
Water Soluble ◽  
Rat Liver Microsomes ◽  
Cytochrome B5 Reductase ◽  
Nadh Cytochrome

NADH-cytochrome b5 reductases of rat liver microsomes, mitochondria, and heavy and light Golgi fractions (GF3 and GF 1+2) were compared by antibody inhibition and competition experiments, by peptide mapping, and by CNBr fragment analysis. The water-soluble portion of the microsomal enzyme, released by lysosomal digestion and purified by a published procedure, was used to raise antibodies in rabbits. Contaminant antimicrosome antibodies were removed from immune sera by immunoadsorption onto the purified antigen, and the F(ab')2 fragments of the pure antireductase antibody thus obtained were found to inhibit the NADH-cytochrome c reductase activity equally well in the four membrane fractions investigated, with similar dose-response relationships. Moreover, the purified water-soluble fragment of microsomal reductase, which by itself is very inefficient in reducing cytochrome c, competed for antibody binding with the membrane-bound enzymes, and therefore prevented the inhibition of their activity not only in microsomes but also in the other fractions. The reductases isolated from detergent-solubilized microsomes, mitochondria, GF3, and GF1+2 by immunoadsorption had identical mobilities in SDS polyacrylamide gels. The corresponding bands were eluted from gels, fragmented with pepsin or CNBr treatment, and the two families of peptides thus obtained were analyzed by two-dimensional mapping and SDS polyacrylamide gel electrophoresis, respectively. Both analyses failed to reveal differences among reductases of the four fractions. These findings support the hypothesis that NADH-cytochrome b5 reductase in its various subcellular locations is molecularly identical.

Metabolic Analysis of Triptolide Microspheres in Human, Dog, Rabbit and Rat Liver Microsomes with UPLC-MS/MS Method

2020 ◽  
Vol 17 ◽  
Author(s):  
LiJuan Wang ◽  
Yan Liu ◽  
Rui Li ◽  
DongXian He
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Internal Standard ◽  
Gradient Elution ◽  
Rat Liver Microsomes ◽  
Good Precision ◽  
Kinetics Parameters ◽  
Measure Concentration ◽  
Standard Curve ◽  
Variation Of Parameters

Objectives: Triptolide (TPL) has been shown to have a good clinical effect on rheumatoid arthritis (RA). We designed TPL microspheres (TPL-MS) and investigated its metabolic behavior in human, dog, rabbit and rat liver microsomes (HLM, DLM, RLM and SDRLM) with UPLC-MS/MS method. Methods: First, a UPLC-MS/MS method was established to measure concentration of TPL in samples. The sample was separated on a C18 column (2.1×100 mm, 1.8μm) and eluted with a gradient elution. The precursor ion/product ion were m/z 378.1/361.0 for TPL and 260.0/116.2 for the internal standard. Then T1/2, Vmax and CLint were calculated from the above data. Finally, the metabolites of TPL-MS were identified by high-resolution UPLC-MS/MS. The sample was separated on a C18 column (2.1×100 mm, 2.2 μm) and eluted with isocratic elution. Mass spectrometric detection was carried out on a thermo Q-exactive mass spectrometer with HESI. The scanning range of precursor ions was from m/z 50 to m/z 750. Result and Discussion: Through several indicators including standard curve, precision, accuracy, stability, matrix effect and recovery rate, the enzymatic kinetics parameters including T1/2, Vmax and CLint were completed. Several metabolites of TPL-MS were identified. Conclusion: UPLC-MS/MS method is an accurate and sensitive method for determination of TPL in liver microsome samples with good precision, accuracy and stability. The variation of parameters indicated that the microspheres can delay the elimination of TPL in liver microsomes. The metabolism of TPL-MS varied among species, but no new metabolites appeared.

scholarly journals The metabolism of gelsevirine in human, pig, goat and rat liver microsomes

2021 ◽  
Author(s):  
Hua‐Hai Zhang ◽  
Wen‐Jia Yang ◽  
Ya‐Jun Huang ◽  
Wen‐Jing Li ◽  
Shuo‐Xin Zhang ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes
Sign in / Sign up

Export Citation Format

Share Document