PHARMACOKINETICS, PHARMACODYNAMICS AND DRUG METABOLISM
Species Differences of Inhibitory Effects on P‐glycoprotein‐mediateD Drug Transport

https://doi.org/10.1002/jps.20787Get rights and content

Abstract

Previously, we clarified the species differences in P‐glycoprotein (P‐gp)‐mediated drug transport activity using human MDR1, monkey MDR1, canine MDR1, rat MDR1a, rat MDR1b, mouse mdr1a, and mouse mdr1b transfected LLC‐PK1 cell lines. However, the species differences in the inhibitory effects on P‐gp‐mediated drug transport have not been clarified yet. The purpose of the present study was to evaluate the species differences in the inhibitory effects of typical P‐gp inhibitors, quinidine and verapamil, on P‐gp‐mediated drug transport using MDR1 transfected cell lines. The transcellular transport of [3H]daunorubicin, [3H]digoxin, and [mebmt‐β‐3H]cyclosporin A across monolayers of the MDR1 transfected cells were measured in the presence or absence of P‐gp inhibitors. On daunorubicin transport, the relative IC50 value (quinidine IC50/verapamil IC50) of human P‐gp was 5.25 and those from other species ranged from 0.89 to 10.70. The transport of digoxin and cyclosporin A also showed different relative IC50 values among human, monkey, canine, rat, and mouse P‐gps. The present study revealed that species differences in the inhibitory effects on P‐gp‐mediated drug transport should not be disregarded among human, monkey, canine, rat, and mouse. This study will provide useful information for predicting drug interactions mediated by P‐gp.

Section snippets

INTRODUCTION

P‐glycoprotein (P‐gp) encoded by multidrug resistance 1 (MDR1) was found to be an energy‐dependent efflux transporter driven by ATP hydrolysis in Chinese hamster ovary cell mutants.1., 2., 3. P‐gp is localized in the apical membrane of cells4 and can transport a variety of compounds including drugs. Since P‐gp exhibits broad substrate specificity, P‐gp expressing cells show cross‐resistance to diverse drugs. In addition, since P‐gp is expressed not only in tumor cells but in normal tissue such

Materials

[3H]Daunorubicin (303.4 or 592.0 GBq/mmol) and [3H]digoxin (358.4 GBq/mmol) were purchased from PerkinElmer Life Sciences (Boston, MA). [mebmt‐β‐3H]Cyclosporin A (296.0 GBq/mmol) was obtained from Amersham Biosciences (Buckinghamshire, UK). Colchicine, quinidine sulfate dihydrate, and verapamil hydrochloride were purchased from Wako Pure Chemical Industries (Osaka, Japan). All other materials were of the highest purity available.

Cell Culture

The MDR1 transfected cell lines designated as hMDR1 (human MDR1),

Effect of Quinidine and Verapamil on P‐gp‐Mediated Drug Transport in MDR1 Transfected Cells and Mock Cells

The transcellular transports of daunorubicin in the presence of quinidine and verapamil, which are known as P‐gp inhibitors, are shown in Figures 1 and 2. In the MDR1 transfected cells, the basolateral‐to‐apical transport of daunorubicin was decreased, while the apical‐to‐basolateral transport was increased by quinidine and verapamil in a concentration‐dependent manner. On the other hand, in the mock cells, the transcellular transport of daunorubicin did not change in the presence of inhibitors.

DISCUSSION

It is increasingly recognized that drug transporters as well as drug metabolizing enzymes also play important roles in drug absorption, distribution, and excretion. The functions of the transporter proteins have been characterized by in vitro and in vivo experiments using tumor cells, transporter protein overexpressing cells, or gene‐knockout animals.8 The efflux drug transporter P‐gp is the best studied among ATP‐binding cassette drug efflux transporters to date. P‐gp was clarified to play key

Acknowledgements

We acknowledge Mr. Brent Bell for reviewing the manuscript.

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    Published online in Wiley InterScience (www.interscience.wiley.com).

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