[29] Assay of formaldehyde generated during microsomal oxidation reactions

Werringloer, J.

doi:10.1016/s0076-6879(78)52031-4

Cited by 124 publications

(44 citation statements)

References 8 publications

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“…The N-dealkylation of erythromycin and ethylmorphine (1 mM final concentration) were measured using 40 mmol/L NADPH, 5 mmol/L MgCl 2 and 1 mg microsomal protein in a final volume of 1 mL of 0.1 m/L phosphate buffer (pH 7.4). After 20 min of incubation at 37 °C in a shaking water bath, the reaction was stopped by adding 250 µL chilled 25% (w/v) trichloroacetic acid; the tubes were then centrifuged (4 °C) and the amount of released formaldehyde in the supernatant was determined with the Nash reagent [59]. The 6ß-and 2ß-hydroxylation of [ 14 C]-testosterone were measured by TLC, modifying the method reported by Larroque et al [27] for progesterone.…”

Section: Total P450 Content Cyp3amentioning

confidence: 99%

Effect of breed and gender on bovine liver cytochrome P450 3A (CYP3A) expression and inter-species comparison with other domestic ruminants

et al. 2005

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-The cytochrome P450 (P450) superfamily represents a group of relevant enzymes in the field of drug metabolism and several exogenous or constitutional factors contribute to regulate its expression. Cattle represent an important source of animal-derived food-products and studies concerning the P450 expression are needed for the extrapolation of pharmacotoxicological data from one species to another and for the evaluation of the consumer's risk associated with the consumption of harmful residues found in foodstuffs. In the present study, possible breed-, genderand species-differences in P4503A (the P450 subfamily more expressed in the human liver) expression were studied in vitro in Piedmontese (PDM) and Limousin (LIM) meat cattle breeds of both sexes and in domestic Ruminants (cattle, sheep and goats). Cytochrome P450 and P4503A contents as well as CYP3A-dependent drug metabolising enzymes (DME) were measured in liver microsomes. Significant lower levels of P450 (P < 0.001) and P4503A (P < 0.05) contents were observed in PDM vs. LIM of both sexes; the P4503A-dependent DME activities were significantly (P values ranging from 0.05 up to 0.001) higher in PDM cattle, particularly in males. A gendereffect in DME activities was noticed (P < 0.05) only in PDM male cattle. With regards to the species, the expression of both P4503A apoprotein and some of the related DME activities were more pronounced in sheep (P < 0.01 vs. cattle) and in goats (P < 0.05 vs. sheep; P < 0.01 vs. cattle) than in cattle. The significant differences in P4503A expression observed in LIM and PDM cattle are consistent with previously published data on strain-and breed-differences pointed out in rats and men. As far as a possible sex-effect is concerned, no clear-cut evidence is likely to be drawn. Finally, P4503A expression was more relevant in small ruminants. ruminants / liver drug metabolism / CYP3A / gender / breed

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Section: Total P450 Content Cyp3amentioning

confidence: 99%

Effect of breed and gender on bovine liver cytochrome P450 3A (CYP3A) expression and inter-species comparison with other domestic ruminants

et al. 2005

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“…Aminopyrine N-demethylase activities (AP demethylase) were assayed as the formation of formaldehyde by the method of Orrenius (29) using 5'-AMP to prevent the breakdown of NADPH by microsomal pyrophosphatase (30). Assay of tetramethylparaphenylenediamine (TMPD) peroxidase activities were performed as described by O'Brien and Rahimtula (31).…”

mentioning

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Age-Related Effects of Heat Stress on Protective Enzymes for Peroxides and Microsomal Monooxygenase in Rat Liver

Ando¹,

Katagiri²,

Yamamoto³

et al. 1997

Environmental Health Perspectives

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To evaluate the age-related response of essential cell fiuctions against peroxidative damage in hyperthermia, we s the bi response to heat stress in both young a aged rats.Passive hyperhermiawas immediately observed in ratsafter ex e to tenvionments. In aged rats, the rctal temperature mntaned thermal homeostais and increased to the same degee as in young rats. in these aged animals, the daage from heat stres was more serious tha '

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“…Rates of erythromycin, benzphetamine and imipramine metabolism were determined by measuring the rate of formaldehyde formation using the Nash reagent (21).…”

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confidence: 99%

Human cytochrome P450 3A4: enzymatic properties of a purified recombinant fusion protein containing NADPH-P450 reductase.

Shet

Fisher

Holmans

et al. 1993

Proc. Natl. Acad. Sci. U.S.A.

112

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Human cytochrome P450 3A4is recognized as the catalyst for the oxygen-dependent metaboism of a diverse group of medicafly important chemicals, inWuding the immunosuppressive agent cyclosporin; macrolide antibiotics, such as erythromycin; drugs such as benzphetamine, nifedipine, and cocaine; and steroids, such as cortisol and testosterone to name but a few. We have engineered the cDNA for human cytochrome P450 3A4 by linkage to the cDNA for the rat or human flavoprotein, NADPH-P450 reductase (NADPH:ferrihemoprotein oxidoreductase, EC 1.6.2.4). An enzymaticafly active fusion protein (rF450[mHum3A4/mRatOR]Ll) has been expressed at high levels in Escherichia coli and purified to homogeneity.Enzymatic studies show a requirement for lipid, detergent, and cytochrome bs for the 63-hydroxylation of steroids and the N-oxidation of nifedipine. In contrast, these additions are not required for the N-demethylation of erythromycin or benzphetamine. A spectrophotometricafly detectable metabolite complex of P450 3A4 is formed during the metabolism of triacetyloleandomycin, and this has a pronounced inhibitory effect on the metabolim of both testosterone and erthromycin. These resuits relate to the interpretation of current methods used to assess the in vivo activity of P450 3A4.One ofthe most versatile ofthe cytochrome P450s is the form present in human liver called CYP3A4, which catalyzes the oxidative metabolism of a wide array of different chemicals with markedly different structural characteristics (1). Interest has centered on this P450 since it is reported to be one of the more abundant P450s in human liver (2); it is inducible by a variety of agents including glucocorticoids as well as phenobarbital (3); it appears to play a central role in the metabolism of the immunosuppressive cyclic peptide cyclosporin A as well as macrolide antibiotics, such as erythromycin (4); it also catalyzes the 63-hydroxylation of a number of steroids including testosterone, progesterone, and cortisol (5). Clinical interest relates to the measurement of erythromycin metabolism by a breath test (6) and the presence of6f-hydroxylated steroids in urine (7) as indicators of CYP3A4 function for evaluation of transplant recipients.P450s ofthe 3A family were first characterized by Guzelian and colleagues (8) based on the ability ofthe catabolic steroid pregnenolone-16a-carbonitrile to induce a unique form of P450 (which they called P-450p). They also recognized the ability of the macrolide antibiotic triacetyloleandomycin (TAO) to serve as a powerful inducer of this type of P450-a result of interest because of the known ability of TAO and other compounds to form stable, metabolite-inhibitor complexes with P450 (9). Reconstitution studies using purified P450s of the 3A family have shown the need to include phospholipids, detergents, and cytochrome b5 when testing enzymatic activities (10, 11).

show abstract

[29] Assay of formaldehyde generated during microsomal oxidation reactions

Cited by 124 publications

References 8 publications

Effect of breed and gender on bovine liver cytochrome P450 3A (CYP3A) expression and inter-species comparison with other domestic ruminants

Effect of breed and gender on bovine liver cytochrome P450 3A (CYP3A) expression and inter-species comparison with other domestic ruminants

Age-Related Effects of Heat Stress on Protective Enzymes for Peroxides and Microsomal Monooxygenase in Rat Liver

Human cytochrome P450 3A4: enzymatic properties of a purified recombinant fusion protein containing NADPH-P450 reductase.

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