Microsomes isolation

Madani, S., Paine, M. F., Lewis, L., Thummel, K. E., Shen, D. D., Comparison of CYP2D6 content and metoprolol oxidation between microsomes isolated from human livers and small intestines, Pharm. 

Borlakoglu, J.T., J.P.G. Wilkins, M.P. Quick, C.H. Walker, and R.R. Dils. 1991b. Metabohsm of [14C]4-chlorobiphenyl by hepatic microsomes isolated from razorbills, pigeons and rats. Comp. Biochem. Physiol. 99C 287-291. 

Pohl R, Philpot R, Fonts J Cytochrome P-450 content and mixed-function oxidase activity in microsomes isolated from mouse skin. Drug Metab Dispos 4 442-450, 1976... 

Drug interactions No drug interaction studies have been conducted with Avonex. Other interferons have been found to reduce cytochrome P-450-mediated drug metabolism. Hepatic microsomes isolated from Avonex-treated rhesus monkeys showed no influence on hepatic P-450 enzyme metabolism activity. 

An in vitro study with a C-PBB mixture containing 12 major components found only traces of radioactivity bound to rat liver microsomal macromolecules (Dannan et al. 1978a). Binding, however, was dependent upon the type of microsomes used to activate the PBB mixture. Microsomes isolated from animals pretreated with methylcholanthrene (MC) bound twice the amount of radioactivity compared with controls, whereas activation with phenobarbital (PB) or PBB bound 5 times more radioactivity than control microsomes. Also, the authors showed that no radioactivity was covalently bound to DNA following incubation with C-PBB. The type of microsomes used or the presence or... 

Borlakoglu JT, Wilkins JP. 1993. Metabolism of di-, tri- and tetrabromobiphenyls by hepatic microsomes isolated from control animals and animals treated with Aroclor 1254, a commercial mixture of polychlorinated biphenyls (PCBs). Comp Biochem Physiol C 105(1) 107-112. 

Microsomal monooxygenase inhibitors that form stable inhibitory complexes with P450, such as SKF-525A, piperonyl butoxide, and other methylenedioxphenyl compounds, and amphetamine and its derivatives, can be readily investigated in this way. This is because the microsomes isolated from pretreated animals have a reduced capacity to oxidize many xenobiotics. 

Figure 3. Arrhenius plot of the metabolism of ethoxycoumarin by hepatic microsomes isolated from rats fed a 5% casein diet for 14-days (5AL). Animals whose PSMOS was induced by phenobarbital are denoted at 5AL-PB.

Conjugation of 4-nitrophenol also occurred in cultured skin epithelial cells from humans (Rugstad and Dybing 1975), in isolated rat hepatocytes (Araya et al. 1986 Moldeus et al. 1976 Tonda and Hirata 1983), and in microsomes isolated from dog livers (Nakano et al. 1986). 

Figure 10.12 Gas chromatograms of the reaction products formed upon incubation of microsomes isolated from yeast over-expressing a tobacco terpene hydroxylase gene (panels A C) (CYP71D20) or harboring only the expression vector DNA (control) (B D). Microsomes were incubated with 5-epi-aristolochene (A B) or 1-deoxycapsidiol (C D) in the presence (blue line) or absence (red line) of NADPH. 5-epi-aristolochene, 1-deoxycapsidiol and capsidiol were all verified by MS.58...

Carlile DJ, Zomorodi K, Houston JB. 1997. Scaling factors to relate drug metabolic clearance in hepatic microsomes, isolated hepatocytes, and the intact liver studies with induced livers involving diazepam. Drug Metab Dispos 25 903-911. 

Rats are treated with 120 mg/kg ANIT and Tween-80 in the same amoimt as used for diluting ANIT. Mter approximately 40 h the rats were killed and microsomes isolated as descript above. Here you can see the results of the heme oxygenase activity measurement by using 0.2 ml hemin solution and different amoimts of microsomal solution. The highest activity is measured with 0.1 ml added microsomes and decreases 5 to 9-fold at 0.4 ml added microsomes. So 0.2 ml hemin solution is too little for an increased (more than 0.1 ml) microsomal volume. So HO is rate-limited. 

Microsomes isolated from hepatic tissue appear to retain all of the mixed-function oxidase capabilities of intact hepa-tocytes because of this, microsomal preparations (with the necessary cofactors, e.g.. NADPH. Mg- ) are u.scd frequently for in vitro drug metabolism studies. Because of its membrane-bound nature, the cytochrome P-450 monooxy-gena.se system appears to be housed in a lipoidal environment. This may explain, in part, why lipophilic xenobiotics arc generally good sub.straics for the monooxygenase system. ... 

NR Niemeijer, TK Gerding, RA DeZeeuw. Glucuronidation of labetalol at the two hydroxy positions by bovine liver microsomes. Isolation, purification, and structure elucidation of the glucuronides of labetalol. Drug Metab Dispos 19 20, 1991. 

Another approach that has been used to correct for differences in microsomes isolated from human livers versus individual enzymes expressed in heterologous expression systems involves the application of intersystem extrapolation factors, or ISEFs, that are empirically derived correction factors. 

Ishii, Y. Mukoyama, H. Ohtawa, M. In vitro biotransformation of finasteride in rat hepatic microsomes. Isolation and characterization of metabolites. Drug Metab.Dispos., 1994, 22, 79-84... 

Mohamed AA, Khalil I, Varanini Z and Pinton R (2000) Increase in NAD(P)H-dependent generation of active oxygen species and changes in lipid composition of microsomes isolated from roots of zinc-deficient bean plants. J Plant Nutr 23 285-295. 

Microsomes isolated from shoot tissues of etiolated wheat seedlings (Tritkum aestivum L. var. Olaf) oxidized the sulfonylurea herbicide prosulfuron (CGA 152005). Identification of the major oxidation product as l-(4-methoxy-6-methyl-l,3,5-triazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)-5-hydroxyphenylsulfonyl]-urea 28 was confirmed by proton NMR spectroscopy (Figure 15). Proton NMR spectra of isolated minor oxidation products were not obtained because of insufficient sample size for analysis. However, these products were identified tentatively as l-[4-(hydroxymethyl)-6-methoxy-l,3,5-triazin-2-yl]-3-[2-(3,3,3-trifluoropropyl)phenylsulfonyl] urea 29 and an intermediate oxidation product l-[4-[(hydroxymethyl)oxy]-6-methyl]-l,3,5-triazin-2-yl]-3-[2-(3,3,3-trifluoropropyl)phenylsulfonyl]urea 30, that degraded to l-(4-hydroxy-6-methyl-l,3,5-triazin-2-yl)-3-[2-(3,3,3-trifluoropropyl)phenylsulfonyl]urea 31 <19%JFA3658>. 

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