First-pass midazolam metabolism catalyzed by 1alpha,25-dihydroxy vitamin D3-modified Caco-2 cell monolayers.
J Pharmacol Exp Ther
; 289(2): 1134-42, 1999 May.
Article
em En
| MEDLINE
| ID: mdl-10215697
ABSTRACT
Cytochrome P-450 (CYP) 3A4 accounts for approximately 50% of all P-450s found in the small intestine (Paine et al., 1997) and contributes to the extensive and variable first-pass extraction of drugs such as cyclosporine and saquinavir. We recently demonstrated that CYP3A4 expression in a differentiated Caco-2 subclone is increased when cell monolayers are treated with 1alpha,25-dihydroxy-vitamin-D3 (Schmiedlin-Ren et al., 1997). This improved metabolic capacity permits the in vitro modeling of first-pass intestinal metabolic kinetics. Midazolam (MDZ) 1'-hydroxylation was used as a specific probe for CYP3A-mediated metabolism in modified Caco-2 monolayers. Caco-2 cells were grown to confluence on laminin-coated culture inserts, and then for two additional weeks in the presence of 1alpha,25-dihydroxy vitamin-D3. Cell monolayers were subsequently exposed to MDZ for varying lengths of time and concentrations. The amount of MDZ in the monolayer increased rapidly after apical drug administration, reaching a pseudo steady state within 6 min. The cellular uptake rate was considerably slower after a basolateral dose. By either route of administration, the rate of 1'-hydroxymidazolam formation was stable and linear for 2 h. Under basolateral sink conditions and low apical MDZ dosing concentration (1-8 microM), the first-pass extraction ratio was found to be approximately 15%. Higher dosing concentrations led to saturation of the hydroxylation reaction and reduction in the extraction ratio. The modified Caco-2 cell monolayer is an excellent model for studying drug absorption and first-pass intestinal metabolic kinetic processes. In this system, the selective CYP3A probe MDZ was rapidly absorbed, yet extensively metabolized, as is observed in vivo.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Midazolam
/
Calcitriol
Tipo de estudo:
Prognostic_studies
Limite:
Humans
Idioma:
En
Revista:
J Pharmacol Exp Ther
Ano de publicação:
1999
Tipo de documento:
Article
País de afiliação:
Estados Unidos