The major aim of this work is to demonstrate the applicability of micellar electrokinetic capillary chromatography with SDS based pseudostationary phase for the screening of cytochrome P450 inhibitors. In contrast with the other capillary electrophoresis modes the cytochrome P450 reaction mixture thus could be used for the analysis without any pre-treatment. Cytochrome P450 2C9, one of the most important isoforms in human liver, was chosen as a model example for this study in combination with diclofenac as a probe substrate. The inhibitory effect on the given cytochrome P450 reaction was evaluated for two inhibitors with different inhibition potential - strong inhibitor sulfaphenazole and moderate inhibitor ketoconazole. As a result 50% inhibitory concentrations IC(50) and inhibition constants K(i) were evaluated; their values for both inhibitors were in a good agreement with the literature data determined by different methods.

• MeSH
• aromatické hydroxylasy antagonisté a inhibitory   chemie   MeSH
• chromatografie micelární elektrokinetická kapilární metody   MeSH
• diklofenak farmakologie   chemie   MeSH
• financování organizované MeSH
• ketokonazol farmakologie   chemie   MeSH
• lidé MeSH
• molekulární struktura MeSH
• reprodukovatelnost výsledků MeSH
• sulfafenazol farmakologie   chemie   MeSH
• systém (enzymů) cytochromů P-450 antagonisté a inhibitory   chemie   MeSH
• Check Tag
• lidé MeSH

Cytochrome P450 2C9 (CYP2C9) is one of the most important isoforms in human liver involved in the metabolism of a large number of therapeutic agents. The aim of this paper is to demonstrate the applicability of CE for the determination of the enzymatic activity of CYP2C9 with diclofenac as a probe substrate. MEKC with SDS as a pseudostationary phase was used for this purpose. Compared to other assays, the MEKC-based method is rapid, can be automated and requires only a small quantity of enzymes and substrate. Moreover, the enzymatic reaction can be monitored with high sensitivity and repeatability even when the reaction mixture is used for the analysis without any pretreatment. The kinetic study on the given enzymatic reaction was also performed since the basic characterization of drug biotransformation generally begins with the enzyme kinetic analysis of metabolite formation. As a result, the Michaelis constant and maximum reaction velocity were evaluated, the values 3.44 +/- 0.45 microM and 19.78 +/- 0.76 nmol min(-1) nmol(-1), respectively, were in agreement with the literature data. On the other hand, a slight deviation from typical Michaelis-Menten kinetics with a weak positive cooperativity was found at diclofenac concentrations below 2 microM. The same atypical kinetic behavior of CYP2C9 was also observed by other authors.

• MeSH
• aromatické hydroxylasy metabolismus   MeSH
• chromatografie micelární elektrokinetická kapilární metody   MeSH
• diklofenak izolace a purifikace   metabolismus   MeSH
• financování organizované MeSH
• kinetika MeSH
• lidé MeSH
• rekombinantní proteiny metabolismus   MeSH
• reprodukovatelnost výsledků MeSH
• senzitivita a specificita MeSH
• Check Tag
• lidé MeSH

A new, simple, rapid, sensitive, and repeatable isocratic reverse-phase HPLC method was developed and validated for simultaneous determination of midazolam and its main three hydroxylated metabolites, i.e. 1'-hydroxymidazolam, 4-hydroxymidazolam, and 1',4-dihydroxymidazolam in rat liver perfusate and also plasma. Diazepam was used as an internal standard to ensure precision and accuracy of this method. Analytes were extracted from alkalinized samples into diethyl ether using single-step liquid-liquid extraction. A C18 analytical column and a mobile phase composed of acetonitrile and sodium acetate buffer were used for the chromatographic separation with UV detection. Limits of detection varied between 7.9 and 19.6 microg/L for midazolam and its hydroxy metabolites. The overall recovery for the analytes exceeded 92%, for concentrations twice the limits of detection. The intra- and inter-day precision at three different concentrations never exceeded 8 and 11% variation, respectively. This method is applicable for modeling and description of possible pharmacological interactions on rat (CYP3A1/2) or human (CYP3A4/5) cytochrome P450 enzymes.

• MeSH
• financování organizované MeSH
• hypnotika a sedativa analýza   krev   MeSH
• krysa rodu rattus MeSH
• midazolam analýza   krev   MeSH
• perfuze MeSH
• potkani Wistar MeSH
• referenční standardy MeSH
• reprodukovatelnost výsledků MeSH
• senzitivita a specificita MeSH
• spektrofotometrie ultrafialová MeSH
• vysokoúčinná kapalinová chromatografie metody   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH