Fig. 5.

Influence of membrane potential on PMAT-mediated adenosine uptake. Vector-transfected and PMAT-expressing cells were incubated with [³H]adenosine (1 μM) for 1 min at 37°C in the presence of 0.5 μM NBMPR. Ba²⁺ was added to block the potassium channels. To avoid precipitation of barium by sulfate and phosphate in the KRH buffer, a chloride salt-based buffer (5 mM glucose, 145 mM NaCl, 3 mM KCl, 1 mM CaCl₂, 0.5 mM MgCl₂, and 5 mM HEPES, pH 7.4) with different compositions of potassium and sodium was used. Each value represents mean ± S.D. (n = 3). *, p < 0.01, significantly different from activity tested in PMAT-transfected cells under normal physiological conditions.