Figure 1. 1-EBIO activates CFTR-mediated basal and cholinergic Cl⁻ secretion in human rectal biopsies.

(A,B) Original recordings of effects of 1-EBIO (500 µM, basolateral) on basal and carbachol-induced (CCH) transepithelial voltage (V_te) and transepithelial resistance (R_te) across rectal biopsies from a control subject (A) and a CF patient carrying two severe CFTR mutations (R1158X/2183AA>G). (B) Experiments were performed in the presence of amiloride and indomethacin. Lumen-positive V_te responses reflect K⁺ secretion and lumen-negative responses reflect Cl⁻ secretion. R_te was determined from V_te downward deflections obtained by pulsed current injection. (C) Summary of effects of 1-EBIO on basal equivalent short-circuit current (I_sc') in rectal biopsies from control subjects and CF patients with no detectable Cl⁻ secretion (CF_absent). (D,E) Effects of 1-EBIO on CCH-induced peak (open bars) and plateau (closed bars) I_sc' responses in control (D) and CF_absent rectal tissues (E). (F,G) Effect of CFTR_inh-172 on 1-EBIO-induced Cl⁻ secretion (lumen-negative I_sc') under basal conditions (F) and on carbachol-induced (CCH) Cl⁻ secretion in the presence of 1-EBIO (G) in rectal biopsies from control subjects. Data are presented as mean±SEM. n = 7–13 individuals per group. * P<0.001 and ^† P<0.01.