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Increased cation transport in mdr1-gene-expressing K562 cells
T Brismar1, A Gruber, C Peterson
1Department of Clinical Neurophysiology, University Hospital, Linköping, Sweden.
Cancer Chemotherapy and Pharmacology
|January 1, 1995
Summary
Multidrug-resistant cells exhibit enhanced cation transport via an ouabain-resistant mechanism. This improved transport is linked to P-glycoprotein expression but not directly to multidrug resistance reversal agents.
Area of Science:
- Cell Biology
- Biochemistry
- Pharmacology
Background:
- Multidrug resistance (MDR) is a significant challenge in cancer chemotherapy.
- P-glycoprotein, encoded by the mdr1 gene, is a key mediator of MDR.
- Cation transport mechanisms may be altered in MDR cells.
Purpose of the Study:
- To compare cation-transport properties in K562 leukemia cells and their MDR sublines.
- To investigate the role of P-glycoprotein in cation transport.
- To determine if altered cation transport is functionally related to MDR.
Main Methods:
- Utilized the potassium analogue thallium (201Tl) to assess cellular accumulation.
- Measured thallium uptake rates in the presence and absence of ouabain (Na-K-ATPase inhibitor).
- Investigated the effect of bumetanide (Na-K-Cl cotransport inhibitor) and MDR-reversing agents.
Main Results:
- MDR sublines (K562/Vcr30, K562/Vcr150) showed significantly higher ouabain-resistant thallium uptake compared to parental K562 cells.
- Vmax for ouabain-resistant uptake increased in MDR cells, with a lower Km.
- Bumetanide inhibited elevated thallium uptake in K562/Vcr150 cells, suggesting involvement of Na-K-Cl cotransport.
Conclusions:
- P-glycoprotein-positive cells possess a more efficient ouabain-resistant cation-transport mechanism.
- This enhanced cation transport is not directly linked to the reversal of multidrug resistance by common agents.
- The findings suggest a distinct functional role for cation transport in P-glycoprotein-expressing cells.