Interplay between CYP3A-mediated metabolism and polarized efflux of terfenadine and its metabolites in intestinal epithelial Caco-2 (TC7) cell monolayers

Pharm Res. 1999 May;16(5):625-32. doi: 10.1023/a:1018851919674.


Purpose: To further characterize cytochrome P450 (CYP) and P-glycoprotein (Pgp) expression in monolayers of the Caco-2 cell clone TC7, a cell culture model of the human intestinal epithelium. To study the interplay between CYP3A and Pgp as barriers to intestinal drug absorption in TC7 cells using terfenadine and its metabolites as substrates.

Methods: mRNA expression of eight CYPs and Pgp was investigated in TC7 and parental Caco-2 (Caco-2p) cell monolayers using RT-PCR. The CYP3A kinetics was determined in microsomes from both cell lines. The transport, metabolism and efflux of terfenadine and its metabolites were investigated in TC7 monolayers.

Results: Both TC7 and Caco-2p cells expressed mRNA for Pgp and several important CYPs. However, mRNA for CYP3A4 was detectable anly from TC7 cells. The relative affinity of CYP3A for terfenadine metabolism in the two cell lines was comparable, but the maximum reaction rate in the TC7 cells was 8-fold higher. The rate of transport of terfenadine and its metabolites hydroxy-terfenadine (HO-T) and azacyclonol across TC7 monolayers was 7.1-, 3.5- and 2.1-fold higher, respectively, in the basolateral to apical direction than it was in the apical to basolateral (AP-BL) direction. Inhibition studies indicated that the efflux was mediated by Pgp. Ketoconazole increased the AP-BL transport terfenadine dramatically by inhibiting both terfenadine metabolism and Pgp efflux.

Conclusions: Cell culture models such as TC7 provide qualitative information on drug interactions involving intestinal CYP3A and Pgp.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / antagonists & inhibitors
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Anti-Anxiety Agents / pharmacokinetics
  • Antifungal Agents / pharmacology
  • Aryl Hydrocarbon Hydroxylases*
  • Biological Transport / drug effects
  • Caco-2 Cells / cytology
  • Caco-2 Cells / drug effects*
  • Caco-2 Cells / enzymology*
  • Calcium Channel Blockers / pharmacology
  • Catalytic Domain
  • Cell Polarity / drug effects
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme Inhibitors
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism*
  • Digoxin / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / enzymology
  • Gene Expression
  • Histamine H1 Antagonists / chemistry
  • Histamine H1 Antagonists / pharmacokinetics*
  • Humans
  • Hydroxylation
  • Intestinal Mucosa / metabolism
  • Intestines / cytology
  • Ketoconazole / pharmacology
  • Kinetics
  • Oligonucleotide Probes
  • Oxidoreductases, N-Demethylating / antagonists & inhibitors
  • Oxidoreductases, N-Demethylating / genetics
  • Oxidoreductases, N-Demethylating / metabolism*
  • Piperidines / pharmacokinetics
  • RNA, Messenger / analysis
  • Terfenadine / chemistry
  • Terfenadine / pharmacokinetics*
  • Tritium
  • Verapamil / pharmacology


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Anti-Anxiety Agents
  • Antifungal Agents
  • Calcium Channel Blockers
  • Cytochrome P-450 Enzyme Inhibitors
  • Enzyme Inhibitors
  • Histamine H1 Antagonists
  • Oligonucleotide Probes
  • Piperidines
  • RNA, Messenger
  • Tritium
  • azacyclonol
  • Digoxin
  • Terfenadine
  • Cytochrome P-450 Enzyme System
  • Verapamil
  • Aryl Hydrocarbon Hydroxylases
  • Cytochrome P-450 CYP3A
  • Oxidoreductases, N-Demethylating
  • Ketoconazole