RESUMO
Cytochromes P450 (CYP) belong to the most important biotransformation enzymes, therefore, their inhibition may lead to serious pharmacological and toxicological consequences. Albendazole (ABZ) is a benzimidazole anthelmintic widely used in human and veterinary medicine. The effects of ABZ on CYP were investigated on the rat (Rattus norvergicus) and mouflon (Ovis musimon) hepatic microsomes. Besides ABZ, its two main metabolites (albendazole sulfoxide, ABZSO, and albendazole sulfone, ABZSOO) were tested to clarify which compound is responsible for the inhibitory effect. After preincubation of microsomes with the benzimidazoles (1, 5 and 25 microM), CYP activities, ethoxyresorufin O-deethylase (EROD) and benzyloxyresorufin O-dearylase activities were measured. The results showed that both ABZ and ABZSO, but not ABZSOO, exhibited significant potency to inhibit CYP activities measured in both tested species. Since ABZ as well as ABZSO are known inducers of EROD activity, our results clearly demonstrate that the drug can act as inducer and also as inhibitor of the same enzyme. In in vitro studies the CYP inhibition may mask the CYP induction. The extent of inhibition observed in mouflon was significantly higher than in rat. This finding emphasizes the importance of performance of inhibition studies in target animal species. Possible consequences of CYP inhibition should be taken into account during the anthelmintic therapy of mouflons with ABZ.
Assuntos
Albendazol/farmacologia , Anti-Helmínticos/farmacologia , Citocromo P-450 CYP1A1/antagonistas & inibidores , Citocromo P-450 CYP2B1/antagonistas & inibidores , Microssomos Hepáticos/efeitos dos fármacos , Albendazol/análogos & derivados , Albendazol/metabolismo , Animais , Anti-Helmínticos/metabolismo , Biotransformação , Citocromo P-450 CYP1A1/metabolismo , Citocromo P-450 CYP2B1/metabolismo , Masculino , Microssomos Hepáticos/enzimologia , Ratos , Ratos Wistar , Carneiro Doméstico , Especificidade da EspécieRESUMO
The promising new drug quinlukast, 4-(4-(quinoline-2'-yl-methoxy)phenylsulphanyl)benzoic acid (VUFB 19363), is under investigation for its anti-inflammatory and anti-asthmatic effects. The main metabolite of quinlukast identified in incubations of rat microsomal fraction, and in primary culture of rat hepatocytes, is quinlukast sulfoxide (M2). Also, several other metabolites of quinlukast were found: two dihydrodiol derivatives (M3, M5) and quinlukast sulfone (M4). This study was conducted to characterize the enzymes involved in quinlukast biotransformation in rat in-vitro. Primary cultures of rat hepatocytes were treated with inducers of different cytochrome P450s (CYPs) for 48 h. Quinlukast (100 microM) was incubated for 24 h in a primary culture of induced or control hepatocytes. The effects of CYP inhibitors, ketoconazole, methylpyrazole, metyrapone and alpha-naphthoflavone (2, 10, 50 microM), on quinlukast metabolism were tested in induced and control hepatocytes. Significant induction of M2 (6 times), M5 (twice) and M3 (by 50%) formation by dexamethasone and strong concentration-dependent inhibition by ketoconazole indicated that CYP3A participates in formation of these metabolites. CYP1A catalyses formation of metabolite M3 mainly, as beta-naphthoflavone induced (10 times) production of M3 and a strong inhibitory effect of alpha-naphthoflavone on its formation was observed. A significant inhibitory effect of quinlukast (2, 10, 50 microM) on ethoxyresorufin, methoxyresorufin and benzyloxyresorufin O-dealkylase activity was observed as well.
Assuntos
Sistema Enzimático do Citocromo P-450/metabolismo , Hepatócitos/enzimologia , Antagonistas de Leucotrienos/farmacocinética , Microssomos Hepáticos/enzimologia , Quinolinas/farmacocinética , Animais , Hidrocarboneto de Aril Hidroxilases/antagonistas & inibidores , Hidrocarboneto de Aril Hidroxilases/metabolismo , Hidrocarboneto de Aril Hidroxilases/farmacocinética , Biotransformação/efeitos dos fármacos , Biotransformação/fisiologia , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Remoção de Radical Alquila/efeitos dos fármacos , Indução Enzimática/efeitos dos fármacos , Indução Enzimática/fisiologia , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Isoenzimas/metabolismo , Masculino , Microssomos Hepáticos/efeitos dos fármacos , Oxigenases/antagonistas & inibidores , Oxigenases/metabolismo , Oxigenases/farmacocinética , Ratos , Ratos Wistar , Sulfóxidos/química , Sulfóxidos/metabolismoRESUMO
Knowledge of the biotransformation processes of veterinary drugs and food supplements in food-producing animals is increasingly important. Residual levels of parent compounds or their metabolites in food of animal origin may differ with the breed, breeding conditions, and gender of animals. The nonsteroidal antiinflammatory drug flobufen, 4-(2',4'-difluorobiphenyl-4-yl)-2-methyl-4-oxobutanoic acid (racemic or its individual enantiomers) was used as a model to evaluate differences in activity, stereoselectivity, and stereospecificity of reductases in primary cultures of hepatocytes from intact male or castrated male domestic pigs (Sus scrofa domestica) or male wild pig (Sus scrofa scrofa). Time-dependent consumption of flobufen enantiomers and formation of dihydroflobufen (DHF) diastereoisomers as their principal metabolites in hepatocytes were measured using chiral HPLC. Flobufen reduction in hepatocytes from all three experimental groups of animals was stereoselective ((+)-R-flobufen was predominantly metabolized) and stereospecific (2R;4S-DHF and 2S;4S-DHF diastereoisomers were preferentially formed). Flobufen reductases activity in male domestic pigs was 30 times higher compared to castrated pigs. Flobufen reductases activity was similar in domestic and wild pigs. The stereospecificity and stereoselectivity of DHF production did not significantly differ with breed or castration of animal. Chiral inversion of flobufen enantiomers was also studied and differences between castrated and intact male pigs were seen.