## Drug induced effect on TER with respect to the initial baseline.

TER values at baseline are plotted against values obtained after the cumulative addition of the different drugs. The hypotenuse of the shaded triangular area represents the line of identity, while magnifications are shown in the box inserts. (A-I) The initial baseline TER values (closed grey circles) are plotted against the values obtained after addition of FSK (n = 44), (B-I) FSK+CFTR_{Inh172} (n = 44) and (C-I) FSK+CFTR_{Inh172}+AMI (n = 44); line of regression is shown as a dashed line with 99% CI (grey vertical bars). In D-I same data as in C-I showing two distinct populations of amiloride responders designated as LOW (closed grey circles-black dashed regression line +99% CI vertical bars, n = 31) and HIGH (open squares, black regression line +99% CI dotted line, n = 13). (A-II) The initial baseline TER values (closed grey circles) are plotted against the values obtained after addition of amiloride; line of regression is shown as a dashed line with 99% CI (grey vertical bars). In B-II same data as in A-II showing two distinct populations designated as LOW (n = 57) and HIGH (n = 24) amiloride responders. Changes in TER with cumulative drug addition of (C-II) AMI+FSK (LOW n = 56, HIGH n = 24) and (D-II) AMI+FSK+CFTR_{Inh172} (LOW n = 56, HIGH n = 21). Additional regression and statistical analysis data are shown in Table B in S1 File.