Received for publication March 11, 2009.
Revised June 2, 2009.
Accepted for publication June 4, 2009.

Culture period-dependent change of function and expression of ABC transporters in Caco-2 cells

Abstract

The objective of this study was to determine an appropriate culture period to assess whether a compound of interest is transported by efflux transporters such as human multidrug resistance 1 (hMDR1), human multidrug resistance-associated protein 2 (hMRP2) and human breast cancer resistance protein (hBCRP) in Caco-2 cells. Caco-2 cells were cultured on a transwell for 1-6 weeks (w). The expression of these transporters in the mRNA and protein levels was examined using a Real-Time polymerase chain reaction and western blotting, respectively. Transcellular transport activities using digoxin, ochratoxin A, olmesartan and estrone-3-sulfate were also examined. Except for digoxin, the permeability co-efficient (P_app) ratio of the three compounds at 2 w was the highest in the periods tested. The P_app ratio of digoxin at 2 w was higher than that at 3 w. The temporal expression profile of each transporter in the mRNA level was similar to that in the protein level, and the functions of hMRP2 and hBCRP were roughly correlated with the expression in the mRNA and protein levels, but not hMDR1. These data suggest that among all the culture periods evaluated a 2 w culture is the best culture period for transport studies to identify whether a compound is a substrate for hMDR1, hMRP2 and hBCRP.

Key words: ABC transporters, absorption, drug transport, intestinal transport