title: Mechanism of high K+ and Tl+ uptake in cultured human glioma cells.
abstract: 1. The aim of this study was to elucidate if the K+ uptake was higher in cultured human glioma cells than in cells from other malignant tumors and to analyze the importance of membrane potential and K+ channels for the uptake. 2. K+ transport properties were studied with the isotopes 42K and the K-analogue 201Tl. 3. Comparison with cultured cells from other malignant tumors showed that the specific steady-state accumulation of Tl+ was significantly higher in glioma cells (U-251MG and Tp-378MG). 4. In Ringer's solution at 37 degrees C the rates of K+ and Tl+ uptake were both inhibited by about 55% in ouabain and 60% in furosemide, bumetanide, or Na(+)- or Cl(-)-free medium. This indicated that the routes for K+ and Tl+ uptake were similar and due to Na,K-ATPase-dependent transport and to Na-K-Cl cotransport. 5. About 10% of the uptake was neither ouabain nor bumetanide sensitive. Ba2+, which is known to block inward-rectifying K+ channels and to depolarize glial cells, and other K+ channel blockers (Cs+ and bupivacaine), had no effect on Tl+ uptake. 6. Metabolic inhibition with dinitrophenol reduced the uptake rate to 17%. 7. The washout of Tl+ was unaffected by bumetanide and K+ channel blockers, but dinitrophenol caused a transient increase of 75%, an effect which persisted in the presence of K+ channel blockers. 8. It was concluded that the high specific K+ and Tl+ accumulation in cultured human glioma cells was due not to the presence of inwardly rectifying K+ channels or other identified K+ channels, but to Na,K-ATPase dependent transport and Na-K-Cl cotransport.
authors.affiliation: Department of Clinical Neurophysiology, University Hospital, Linköping, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Brismar
authors.forename: S
authors.initials: S
authors.lastname: Anderson
authors.forename: V P
authors.initials: VP
authors.lastname: Collins
mesh_terms: D001464:Barium / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002045:Bupivacaine / Q000494:pharmacology; D002460:Cell Line; D002586:Cesium / Q000494:pharmacology; D004140:Dinitrophenols / Q000494:pharmacology; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D011197:Potassium Radioisotopes; D013793:Thallium / Q000378:metabolism*; D013794:Thallium Radioisotopes; D014407:Tumor Cells, Cultured; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D004140:Dinitrophenols; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D011197:Potassium Radioisotopes; D013794:Thallium Radioisotopes; D014475:Uncoupling Agents; D002034:Bumetanide; D002586:Cesium; D001464:Barium; D010042:Ouabain; D013793:Thallium; D011188:Potassium; D002045:Bupivacaine