Thallium-201 uptake relates to membrane potential and potassium permeability in human glioma cells.
The mechanism for 201Tl+ uptake was studied in cultured human glioma cell lines. Ouabain (1 mM) decreased the uptake at steady-state to 60%, but the rate of uptake was faster in the presence of ouabain. Addition of non-radioactive Tl+ (to a K+-free medium) decreased the uptake, but much less than expected for a system limited by the number of transport sites. Changes in K+ concentration of incubation medium affected the 201Tl+ uptake as predicted by the electrochemical equilibrium (Nernst equation). Using the uptake in isotonic KCl as a reference for membrane potential (0 mV), the calculated membrane potential was -75 mV in a medium with 3.0 mM K+. The Tl+-flux constants and the membrane permeabilities for Tl+ and K+ were calculated from the rate of uptake and from wash-out experiments. This is a new method for membrane potential and permeability studies in cell populations. The mechanism for 201Tl+ uptake is relevant for the clinical interpretation of 201Tl+ scintigraphy.
Brismar
T
T
Department of Clinical Neurophysiology, Karolinska Hospital, Stockholm, Sweden.
Collins
V P
VP
Kesselberg
M
M
D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism* / Q000502:physiology; D013794:Thallium Radioisotopes / Q000493:pharmacokinetics*; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D014634:Valinomycin / Q000494:pharmacology
D013794:Thallium Radioisotopes; D014634:Valinomycin; D010042:Ouabain; D011188:Potassium