Fig. 4. Direct linear plots for Ba²⁺ inhibition of short-circuit current (I_sc). (A) Experiments with NaCl as the mucosal and serosal bathing solution; the mean control value of I_sc was -13.00 µA cm^-2 (the y intercepts are the means for six experiments). (B) Experiments with NaCl and KCl as the mucosal and serosal solutions, respectively (N=4). The mean control I_sc for these experiments was -30.37 µA cm^-2. Note that the lines do not all intersect at a common point as would be predicted if the Ba²⁺ inhibition were due to binding to a single site with a single binding affinity. The broken lines indicate the x intercept in A and B, which is the K_i value for Ba²⁺ inhibition at lower concentrations. In B, the broken horizontal line indicates the blocker-sensitive I_sc (not drawn in A).