Figure 6

The MC3-ISM response is minimally affected by a Cl⁻ channel blocker and Cl⁻ cotransporter inhibitors. (A) Continuous records of the MCS-ISM potential (V_Cl) in response to step changes of [Cl⁻] (1, 2.5, 5, 10, 50, 100 mM) in the absence (black trace) or presence of 100 μM (red trace) and 200 μM (blue trace) 9-ACA. Records for each 9-ACA concentration were obtained consecutively for the same MC3-ISM, but were shifted in time and superimposed to facilitate a visual comparison. Arrows indicate detectable differences from the control response in the absence of 9-ACA. (B) Addition of 20 μM bumetanide (BMT) did not detectably alter the V_Cl response of an MC3-ISM. The test protocol and display of the continuous data were the same as in (A). (C) Addition of 100 μM furosemide (FUR) did not affect the response for Cl⁻ solutions of 5 mM or greater, and mildly attenuated the response in 2.5 and 1 mM solutions (blue arrows). (D–F) Calibration plots of V_Cl as a function of a_Cl shows that a modest shift of V_Cl was detectable only for 200 μM 9-ACA and at the lowest concentration test solution with 0.1 mM Cl⁻. For each drug tested (A–C), similar responses were observed for four different MC3-ISMs. Symbols represent the mean ± SEM for 4 different MC3-ISMs.