PHARMACOKINETICS, PHARMACODYNAMICS AND DRUG METABOLISMEffect of P‐Glycoprotein Expression Levels on the Concentration‐Dependent Permeability of Drugs to the Cell Membrane
Section snippets
INTRODUCTION
The MDR1 gene‐product P‐glycoprotein (P‐gp/ABCB1), an ATP‐dependent efflux pump, plays an essential role in the efflux transport of hydrophobic xenobiotics and peptides from the inside to the outside of cells.1, 2 P‐gp is highly expressed in the plasma membrane in several tumor cells as a mechanism responsible for resistance against certain cytostatic drugs.3, 4 It is also widely expressed in the plasma membrane in normal tissues such as villous epithelial cells in the intestine, endothelial
Materials
Dulbecco's Modified Eagle's Medium with 4500 mg/L glucose (DMEM) and Minimum Essential Medium Eagle (MEME) were purchased from Sigma Chemical Co. (St. Louis, MO). Minimum Essential Medium Alpha Medium with L‐glutamine, ribonucleosides and deoxyribonucleosides (MEMAM), nonessential amino acids (NEAA), fetal bovine serum (FBS), L‐glutamine, trypsin (0.25%)‐EDTA (1 mM), and antibiotic‐antimycotic mixture (10000 U/mL penicillin G, 10000 µg/mL streptomycin sulfate and 25 µg/mL amphotericin B in
Effect of Donor Concentration on Absorptive and Secretory Transport of P‐gp Substrate Drugs
To understand the effect of donor concentration on the transcellular transport of P‐gp substrates drugs, at first, AP to BL and BL to AP permeability of quinidine (one of the typical P‐gp substrates), was determined at various donor concentrations in normal Caco‐2 cells (Fig. 1). At the lower concentration range (below 1 µM), AP to BL permeability of quinidine was low and constant, then increased with an increase in the donor concentration showing a sigmoid‐type relationship to donor
DISCUSSION
P‐gp expressed in normal tissues is known to affect the pharmacokinetic profiles of a variety of drugs by denaturing the absorption, distribution, and excretion. Especially in the intestine, P‐gp‐mediated efflux has been recognized to work as a barrier against the absorption of its substrate drugs after oral administration. In the present study, we investigated the effects of drug concentration and P‐gp expression level on the membrane permeability of P‐gp substrate drugs to establish a
Acknowledgements
The authors would like to thank Dr. Piet Borst of The Netherlands Cancer Institute for kindly providing MDR1‐MDCKII cells. We would like to thank Dr. Yuichi Sugiyama of The University of Tokyo for kindly providing MDR1‐knockdown Caco‐2 cells. The real‐time quantitative PCR was performed in Department of Hospital Pharmacy, School of Medicine, Kobe University, and we are very grateful to Dr. Katsuhiko Okumura and Dr. Toshiyuki Sakaeda for organizing the study and to Ms. Yuka Moriya and Mr.
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