P‐GLYCOPROTEIN EXPRESSION IN CLASSICAL MULTI‐DRUG RESISTANT LEUKAEMIA CELLS DOES NOT CORRELATE WITH ENHANCED CHLORIDE CHANNEL ACTIVITY

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Abstract
SUMMARY: 1. P‐glycoprotein (Pgp) is an ATP‐dependent drug efflux pump responsible for classical multi‐drug resistance (MDR).2. Pgp is part of a supergene family of membrane transport proteins that includes the cystic fibrosis gene product.3. Transfection of cells with the MDRl gene has been previously shown to generate volume‐regulated chloride channel activity in association with Pgp expression.4. We have used whole‐cell patch clamping to examine the drug‐sensitive T lymphoblastic cell line CEM‐CCRF and its classical MDR derivative CEM/VLB100. The results suggest that expression of Pgp is not associated with increased chloride channel activity in this multi‐drug resistant cell line.5. We were unable to confirm previously reported results in MDRl transfected cell lines that suggested that Pgp was associated with the presence of volume‐regulated chloride channels.