The CFTR channel inhibitor GlyH-101 inhibits SLC26A9. (A) HEK 293 cells transfected with SLC26A9 and voltage clamped at −40 mV were exposed to either 50 µM GlyH-101 or 100 µM glibenclamide after a 60-s stabilization period. GlyH-101 inhibited 50% of the constitutive chloride current within seconds and an additional 20% over the course of a 3-min application. The inhibition was partially reversed after 3 min of washout, also with two phases of recovery. The minor drop in current during application of 100 µM glibenclamide was statistically insignificant; longer exposure times and/or higher doses were not explored. Representative tracings of at least three experiments each are shown. (B) Representative I-V behavior of SLC26A9 and CFTR in the presence of the indicated blockers. SLC26A9-transfected cells displayed a mild IR I-V response after 3 min of exposure to either GlyH-101 or glibenclamide. Cells transfected with wtCFTR, stimulated with 10 µM forskolin, and then inhibited with 50 µM GlyH-101 for 3 min displayed a strong IR I-V response. SLC26A9 I-V curves are for traces shown in A, measured at 240 s (solid diamond). All current values are normalized by cell capacitance.