Biosynthesis of 16α,17α-epoxy-4-androsten-3-one in rat liver microsomes

1980 ◽  
Vol 95 (1) ◽  
pp. 58-66 ◽  
Author(s):  
B. Disse ◽  
L. Siekmann ◽  
H. Breuer
Keyword(s):  
Rat Liver ◽  
Styrene Oxide ◽  
Liver Microsomes ◽  
Epoxy Compound ◽  
Male Rat ◽  
Gas Liquid Chromatography ◽  
Rat Liver Microsomes ◽  
Epoxide Hydratase ◽  
Layer Chromatography ◽  
Generating System

Abstract. 4,16-Androstadien-3-one was incubated with the microsomal fraction of male rat liver in the presence of a NADPH generating system and oxygen. The metabolites formed were extracted from the incubation medium and purified by thin-layer chromatography (tic). Final identification was performed by combined gas liquid chromatography-mass spectrometry. Incubation of 4,16-androstadien-3-one resulted in the formation of a non-polar metabolite which proved to be 16α,17α-epoxy-4-androsten-3-one. This epoxide is a shortlived intermediate which is rapidly hydrolysed by the microsomal epoxide hydratase to 16β,17α-dihydroxy-4-androsten-3-one. In order to increase the amounts of epoxide in the incubation mixtures, styrene oxide which is a potent inhibitor of the epoxide hydratase was added. Under these conditions, up to 8% of the 16-dehydro-steroid incubated was transferred to the 16α,17α-epoxy-compound.

Biosynthesis of 16α,17α-epoxy-oestratrienol in rat liver microsomes

1980 ◽  
Vol 95 (1) ◽  
pp. 49-57 ◽  
Author(s):  
L. Siekmann ◽  
P. Thull ◽  
H. Breuer
Keyword(s):  
Reference Material ◽  
Thin Layer ◽  
Rat Liver ◽  
Mass Spectra ◽  
Styrene Oxide ◽  
Liver Microsomes ◽  
Mass Fragmentography ◽  
Rat Liver Microsomes ◽  
Epoxide Hydratase ◽  
Layer Chromatography

Abstract. After incubation of 1,3,5(10),16-oestratetraenol, a 16-dehydrosteroid, with rat liver microsomes, 16α,17α-epoxy-oestratrienol was isolated as metabolite. The compound was detected by the use of mass fragmentography after purification of the incubation extract by thin-layer chromatography. Since the epoxide is rapidly hydrolysed by a hepatic epoxide hydratase, only very small concentrations of this metabolite were present in the incubation extract. When styrene oxide was added to the incubation mixture as inhibitor of the epoxide hydratase, the yield of the steroid epoxide increased considerably. Final identification of the oestrogen epoxide was performed by recording mass spectra and by comparison with authentic reference material.

STUDIES ON THE METABOLISM OF C19 STEROIDS IN RAT LIVER. 6. HYDROXYLATION OF 4-ANDROSTENE-3,17-DIONE IN RAT LIVER MICROSOMES

1970 ◽  
Vol 65 (1) ◽  
pp. 84-94 ◽  
Author(s):  
Jan-Åke Gustafsson ◽  
Belisário P. Lisboa
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Gas Chromatography Mass Spectrometry ◽  
Male Rat ◽  
Rat Liver Microsomes ◽  
Relative Importance ◽  
Adult Male Rat ◽  
Layer Chromatography

ABSTRACT Following incubations of androstenedione with 105 000 × g microsomes of adult male rat liver, 6β-, 6α-, 7α-, 16α-, and 18-hydroxyandrostenedione were isolated by thin-layer chromatography and identified by gas chromatography-mass spectrometry. After incubations with testosterone the only 3,17-dioxo-Δ4-steroids formed were 6β- and 7α-hydroxyandrostenedione. 6β- and 18-Hydroxyandrostenedione were isolated after incubations with 6β- and 18-hydroxytestosterone, respectively. The relative importance of the 17-oxo- and the 17β-hydroxy-pathways in the formation of 3,17-dioxo-Δ4-C19O3 steroids is discussed.

A proteomic method for analysis of CYP450s protein expression changes in carbon tetrachloride induced male rat liver microsomes

Toxicology ◽  
2007 ◽  
Vol 237 (1-3) ◽  
pp. 1-11 ◽  
Author(s):  
Nuan Jia ◽  
Xin liu ◽  
Jun Wen ◽  
Linyi Qian ◽  
Xiaohong Qian ◽  
...  
Keyword(s):  
Carbon Tetrachloride ◽  
Protein Expression ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Male Rat ◽  
Rat Liver Microsomes

Use of recombinant human ferrochelatase as a sensitive bioassay for N-alkylprotoporphyrin IX formed after interaction of porphyrinogenic xenobiotics with rat liver microsomes

2000 ◽  
Vol 78 (7) ◽  
pp. 578-581 ◽  
Author(s):  
Jeremy T Gamble ◽  
Simon GW Wong ◽  
Harry A Dailey ◽  
Gerald S Marks
Keyword(s):  
Cytochrome P450 ◽  
Rat Liver ◽  
Liver Microsomes ◽  
Rat Liver Microsomes ◽  
Bioassay System ◽  
Human Cytochrome ◽  
In Vitro Systems ◽  
Layer Chromatography ◽  
Cyp Isozymes

Several porphyrinogenic xenobiotics elicit mechanism-based inactivation of cytochrome P450 (CYP) isozymes, leading to the formation of N-alkylprotoporphyrin IX (N-alkylPP), a potent inhibitor of ferrochelatase, the terminal enzyme in heme biosynthesis. Recognizing their role in experimental porphyria, our long term objective is the establishment of an appropriate in vitro system for the detection and quantification of N-alkylPPs, formed in human liver after the administration of potential porphyrinogenic compounds. In a previous study, we used a combination of thin-layer chromatography and UV-visible spectrophotometry to isolate and identify N-alkylPPs after incubating porphyrinogenic compounds with rat liver microsomes. However, the overall yield of N-alkylPPs was low, and it was concluded that in vitro systems, such as human lymphoblastoid microsomal preparations containing single cDNA-expressed human cytochrome P450 (CYP) isozymes, do not contain sufficient CYP for in vitro studies designed to isolate N-alkylPP. In the present study we demonstrate that purified recombinant human ferrochelatase (FC) provides an extremely sensitive bioassay system for N-alkylPPs and is capable of detecting N-alkylPP in the 10-6nmol range. Therefore, we propose that this bioassay system might allow the use of human lymphoblastoid microsomal preparations containing single cDNA-expressed human CYP isozymes to detect N-alkylPP produced after mechanism-based (catalysis-based) CYP inactivation. If this is found to be correct it will facilitate identification of potentially porphyrinogenic drugs prior to administration to humans.Key words: ferrochelatase, N-alkylprotoporphyrin IX, porphyria, mechanism-based inactivation.

Stanozolol and danazol, unlike natural androgens, interact with the low affinity glucocorticoid-binding sites from male rat liver microsomes.

Endocrinology ◽  
1994 ◽  
Vol 134 (3) ◽  
pp. 1401-1408 ◽  
Author(s):  
L Fernández ◽  
R Chirino ◽  
L D Boada ◽  
D Navarro ◽  
N Cabrera ◽  
...  
Keyword(s):  
Rat Liver ◽  
Binding Sites ◽  
Liver Microsomes ◽  
Male Rat ◽  
Rat Liver Microsomes

scholarly journals Glucuronidation of the environmental oestrogen bisphenol A by an isoform of UDP-glucuronosyltransferase, UGT2B1, in the rat liver

1999 ◽  
Vol 340 (2) ◽  
pp. 405-409 ◽  
Author(s):  
Hiroshi YOKOTA ◽  
Hidetomo IWANO ◽  
Mari ENDO ◽  
Tsutomu KOBAYASHI ◽  
Hiroki INOUE ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Rat Liver ◽  
Northern Blot Analysis ◽  
Glucuronic Acid ◽  
Liver Microsomes ◽  
Male Rat ◽  
Rat Liver Microsomes ◽  
Crystalline Compound ◽  
Udp Glucuronosyltransferase

Bisphenol A, an environmental oestrogenic chemical, was found to conjugate highly with glucuronic acid in male rat liver microsomes studied in vitro. In the various isoforms tested (1A1, 1A3, 1A5, 1A6, 1A7 and 2B1), glucuronidation of bisphenol A and of diethylstilboestrol, a synthetic crystalline compound possessing oestrogenic activity and known to be glucuronidated by liver microsomes, was catalysed by an isoform of UDP-glucuronosyltransferase (UGT), namely UGT2B1, which glucuronidates some endogenous androgens. UGT activity towards bisphenol A in liver microsomes and in UGT2B1 expressed in yeast AH22 cells (22.9 and 0.58 nmol/min per mg of microsomal proteins respectively) was higher than that towards diethylstilboestrol (75.0 and 4.66 pmol/min per mg of microsomal proteins respectively). UGT activities towards both bisphenol A and diethylstilboestrol were distributed mainly in the liver but were also observed at substantial levels in the kidney and testis. Northern blot analysis disclosed the presence of UGT2B1 solely in the liver, and about 65% of the male rat liver microsomal UGT activities towards bisphenol A were absorbed by the anti-UGT2B1 antibody. These results indicate that bisphenol A, in male rat liver, is glucuronidated by UGT2B1, an isoform of UGT.

scholarly journals Self-augmentation Effect of Male-specific Products on Sexually Differentiated Progesterone Metabolism in Adult Male Rat Liver Microsomes

2000 ◽  
Vol 276 (7) ◽  
pp. 4604-4610 ◽  
Author(s):  
Akihiko Yamada ◽  
Morio Yamada ◽  
Yukihisa Fujita ◽  
Takashi Nishigami ◽  
Keiji Nakasho ◽  
...  
Keyword(s):  
Rat Liver ◽  
Adult Male ◽  
Liver Microsomes ◽  
Male Rat ◽  
Rat Liver Microsomes ◽  
Progesterone Metabolism ◽  
Adult Male Rat ◽  
Male Specific
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