Figure 2. Hyperosmotic conditions inhibit endogenous TRPM7-like MagNuM currents.

A, representative current development of MagNuM inward and outward currents measured in wild-type HEK293 cells. Cells were superfused with hypo-osmotic extracellular solution (□, n = 8) or hypertonic extracellular solutions at 480 mosmol l⁻¹ (^, n = 5) or 880 mosmol l⁻¹ (•, n = 4) as indicated by the black bar. Hypotonic conditions were achieved by removal of NaCl (total of 80 mm NaCl) and hypertonic conditions were established using appropriate amounts of sucrose. Currents were elicited by a voltage ramp from −100 mV to +100 mV over 50 ms at 0.5 Hz intervals. Inward current amplitudes were extracted at −80 mV and outward currents at +80 mV and plotted versus time. Cells were perfused with the standard intracellular Cs-based solution in the absence of Mg·ATP, with 0.9 mm free Mg²⁺ and 10 mm Cs-BAPTA. Baseline correction was done by measuring basal leak currents between 6 s and 22 s from each curve and subtracted from the overall current. B, I–V relationship taken from the same cells as in A just before application of 480 mosmol l⁻¹ (thin trace) and at the end of application (thick trace). Note that I–V data are not basal leak subtracted. C, I–V relationship taken from the same cells as in A just before application of 880 mosmol l⁻¹ (thin trace) and at the end of application (thick trace). Data are not basal leak subtracted. Note that the slightly more negative reversal potential could be due to somewhat more active background channels in this particular cell that are not completely suppressed by intracellular Cs²⁺.