Atorvastatin transport in the Caco-2 cell model: contributions of P-glycoprotein and the proton-monocarboxylic acid co-transporter

Pharm Res. 2000 Feb;17(2):209-15. doi: 10.1023/a:1007525616017.


Purpose: The purpose of this study was to elucidate the mechanisms by which an HMG-CoA reductase inhibitor, atorvastatin (an organic acid with a pKa of 4.46), was transported in the secretory and absorptive directions across Caco-2 cell monolayers.

Methods: Caco-2 cells were grown on polycarbonate membrane inserts in 6-well Snapwell plates (Costar). The permeability of radiolabeled compounds across Caco-2 cell monolayers was determined using a side-by-side diffusion apparatus (NaviCyte) and an automated liquid handler (Hamilton Microlab 2200). The apical uptake of 14C-atorvastatin was also determined in Caco-2 cells. Cyclosporin A (20 microM) was present in the uptake media to block potential P-glycoprotein-mediated atorvastatin efflux.

Results: Polarized permeation of atorvastatin was observed with the basolateral-to-apical (B-to-A) permeability being 7-fold greater than the A-to-B permeability (35.6 x 10(-6) and 4.9 x 10(-6) cm/s, respectively). The secretion of atorvastatin was a saturable process with an apparent Km of 115 microM. The B-to-A permeability of atorvastatin was significantly reduced by cyclosporin A (10 microM), verapamil (100 microM), and a P-glycoprotein specific monoclonal antibody, UIC2(10 microg/ml) (43%, 25%, and 13%, respectively). Furthermore, both CsA and verapamil significantly increased the A-to-B permeability of atorvastatin by 60%; however, UIC2 did not affect the A-to-B permeability of atorvastatin. CsA uncompetitively inhibited the B-to-A flux of atorvastatin with a Ki of 5 microM. In addition, atorvastatin (100 microM) significantly inhibited the B-to-A permeability of vinblastine by 61%. The apical uptake of atorvastatin increased 10.5-fold when the apical pH decreased from pH 7.4 to pH 5.5 while the pH in the basolateral side was fixed at pH 7.4. A proton ionophore, carbonylcyanide p-trifluoro-methoxyphenylhydrazone (FCCP) significantly decreased atorvastatin uptake. In addition, atorvastatin uptake was significantly inhibited by benzoic acid, nicotinic acid, and acetic acid each at 20 mM (65%, 14%, and 40%, respectively). Benzoic acid competitively inhibited atorvastatin uptake with a Ki of 14 mM. Similarly, benzoic acid, nicotinic acid, and acetic acid significantly, inhibited the A-to-B permeability of atorvastatin by 71%, 21%, and 66%, respectively.

Conclusion: This study demonstrated that atorvastatin was secreted across the apical surface of Caco-2 cell monolayers via P-glycoprotein-mediated efflux and transported across the apical membrane in the absorptive direction via a H(+)-monocarboxylic acid cotransporter (MCT). In addition, this study provided the first evidence that negatively charged compounds, such as atorvastatin, can be a substrate for P-glycoprotein.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / pharmacology*
  • Acetic Acid / pharmacology
  • Anion Transport Proteins
  • Antineoplastic Agents, Phytogenic / pharmacokinetics
  • Atorvastatin
  • Benzoic Acid / pharmacology
  • Biological Transport / drug effects
  • Caco-2 Cells / chemistry
  • Caco-2 Cells / metabolism
  • Calcium Channel Blockers / pharmacology
  • Carbon Radioisotopes
  • Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / pharmacology
  • Carboxylic Acids / pharmacokinetics
  • Carrier Proteins / metabolism*
  • Cell Polarity / drug effects
  • Cyclosporine / pharmacology
  • Drug Interactions
  • Heptanoic Acids / chemistry
  • Heptanoic Acids / pharmacokinetics*
  • Humans
  • Hydrogen-Ion Concentration
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors / chemistry
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors / pharmacokinetics*
  • Immunosuppressive Agents / pharmacology
  • Indicators and Reagents / pharmacology
  • Ionophores / pharmacology
  • Niacin / pharmacology
  • Protons
  • Pyrroles / chemistry
  • Pyrroles / pharmacokinetics*
  • Verapamil / pharmacology
  • Vinblastine / pharmacokinetics


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Anion Transport Proteins
  • Antineoplastic Agents, Phytogenic
  • Calcium Channel Blockers
  • Carbon Radioisotopes
  • Carboxylic Acids
  • Carrier Proteins
  • Heptanoic Acids
  • Hydroxymethylglutaryl-CoA Reductase Inhibitors
  • Immunosuppressive Agents
  • Indicators and Reagents
  • Ionophores
  • Protons
  • Pyrroles
  • Niacin
  • Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone
  • Vinblastine
  • Cyclosporine
  • Benzoic Acid
  • Atorvastatin
  • Verapamil
  • Acetic Acid