Fig. 5.

Long-term exposure to extracellular 1 μM curcumin activates a chloride current resembling ICl_swell in isotonic conditions. The chloride current was measured in human renal cells (HEK293 Phoenix) by the patch clamp technique in whole cell configuration. Original recordings obtained in isotonic solution (upper trace) and isotonic solution after addition of 75 μM NPPB (lower trace) in cells incubated 15–23 h in a complete medium containing (a) 1.0 μM curcumin or (b) 0.05% DMSO as a control are shown. Currents were elicited with voltage increments of 20 mV from −120 to +100 mV applied from a holding potential of 0 mV (a, lower right inset). Respective current density-to-voltage relations obtained in isotonic solution (iso) and isotonic solution after addition of NPPB (iso + NPPB) in cells incubated with 1.0 μM curcumin or 0.05% DMSO as a control are shown in (c) and (d), respectively. NPPB inhibited the chloride current by ∼50% in c (p < 0.0001, F test) and was ineffective in d (n.s., F test), indicating that a chloride current was present after incubation with curcumin (c) but not with DMSO (d).