Oxidative drug metabolism via the cytochrome P450 (CYP) system is a principle means of drug clearance. Several decades of studies have pointed to five CYP forms—CYP1A2, 2C9, 2C19, 2D6, and 3A—as those which are primarily responsible for human metabolism of small molecule (MW <1500) drugs and drug-like compounds.1 The absolute levels and CYP enzyme activities vary substantially among individual ...

Buprenorphine (BUP) is a synthetic derivative of the morphine alkaloid thebaine. BUP is metabolized by N-dealkylation to form the active metabolite nor-buprenorphine (Nor-BUP), and both undergo subsequent glucuronidation. Although BUP has been used clinically for years, its metabolism has still not been fully elucidated. The aim of this study was to clarify the identity of the human hepatic cyt...

The peripheral benzodiazepine receptor plays a role in the translocation of cholesterol into mitochondria where steroidogenesis occurs. Sterols have been suggested to be involved in the regulation of the cytochrome P-450 (CYP)2B subfamily as the endogenous suppressor of this CYP. To investigate the role of cholesterol metabolites on the expression of CYPs, the effect of PK11195, a specific liga...

Irinotecan (CPT-11) is a water-soluble analogue of camptothecin showing activity in colon cancer. Recently, we identified a major metabolite of CPT-11 in patients' plasma, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino] carbonyloxycamptothecin (APC), which is produced by the oxidation of the distal piperidine ring (P. Rivory et al, Cancer Res., 56: 3689-3694, 1996). As with all active cam...

To assess the potential effects of persistent organic pollutants (POPs) on the expression of cytochrome P450 (CYP) 2B and 3A isozymes in Baikal seal, the 5′-flanking regions of these CYP genes were isolated, and transactivation analysis was performed by in vitro reporter gene assay system. The 3.2 kbp of CYP2B and 2.2 kbp of CYP3A gene promoter/enhancer regions were cloned and sequenced from Ba...

The inhibitory effects of fluoroquinolones on the enzyme activity, protein levels and mRNA expression of liver cytochrome P450 (CYP) 1A and 3A were investigated in male broiler chicks. Enrofloxacin (20 mg/kg), sarafloxacin (8 mg/kg) and marbofloxacin (5.5 mg/kg) were administrated in drinking water for 7 consecutive days. A cocktail of the probe drugs caffeine and dapsone was used to determine ...

Induction of cytochromes P450 (P450s) by drugs can lead to drug-drug interactions. Primary hepatocytes have been reported to retain inducible P450s. To optimize the use of primary hepatocytes for predicting induction of P450 (CYP 3A and 2B) expression in vivo, both culture conditions and expression of induction potentials were investigated. In rat hepatocytes, basal CYP 3A1/2 expression was bet...

Biotransformation of cerivastatin, a new cholesterol-lowering drug, by human liver microsomes was investigated using the 14C-labeled drug. Metabolite profiles were established by HPLC and structures of metabolites were elucidated. Two metabolic pathways were equally important, demethylation of the benzylic methyl other and hydroxylation at one methyl group of the 6-isopropyl substituent. The pr...

Mulberry is a fruit containing polyphenol antioxidants. Cyclosporine (CSP), a potent immunosuppressant with a narrow therapeutic range, is widely used in transplant patients. This study investigated the effect of co-administration of mulberry on the bioavailability of CSP, a probe drug of P-glycoprotein (P-gp)/cytochrome P450 3A4 (CYP 3A4), in rats and relevant mechanisms. CSP (2.5 mg/kg) was o...