Responses of forskolin-stimulated currents to blockers in HEK 293 cells expressing wtCFTR ± SLC26A9. (A) HEK 293 cells expressing wtCFTR alone were stimulated with forskolin and allowed to reach a plateau, and then inhibited with either glibenclamide or GlyH-101; the latter rapidly and almost completely inhibited wtCFTR alone. V_H = −40 mV. (B) I-V curves measured 90 s after the addition of blocker (330 s in A) demonstrate the opposite voltage dependence of the two blockers. (C) HEK 293 cells coexpressing SLC26A9 and wtCFTR were stimulated with forskolin and allowed to reach a plateau, and then inhibited with either glibenclamide or GlyH-101. V_H = −40 mV. (D) The I-V curves measured 90 s after the addition of blocker (330 s in C) demonstrate the opposite voltage dependencies of the two blockers. The nonlinearity or voltage dependence of the block of wtCFTR alone (B) is greater than evidenced in the coexpressors (see Table I for mean values).