Figure 7. Sodium feedback inhibition is at least partially preserved in colon tissue of L/L mice.

The experimental protocol was similar to that described in Fig. 6. Tissue preparations were pre-incubated for 8 h using an apical low sodium (4 mm) bath solution. A, representative I_SC traces from colon tissue of WT or L/L animals are shown. To investigate sodium feedback inhibition, I_SC was monitored for 60 min after increasing the NaCl concentration in the apical bath solution to 63.5 mm (as indicated by the bar below the traces). ΔI_SC-Ami was estimated at time zero (t₀) immediately after switching the apical bath solution from 4 mm to 63.5 mm NaCl and 60 min later (t₆₀) when 10⁻⁴m amiloride (Ami) were applied as indicated by the black bar. The I_SC traces, shown as dashed lines, represent control experiments in which colon tissues were pre-incubated with an apical bath solution containing 63.5 mm NaCl. Mock solution exchanges were performed at t₀ to demonstrate that a solution exchange per se has no significant effect on I_SC. B, summary of experiments as shown in A. Each circle or square represents an individual ΔI_SC-Ami value estimated at time zero (t₀; open symbols) or after 60 min (t₆₀; filled symbols) in colon tissue from WT (circles) or L/L (squares) animals. ΔI_SC-Ami values measured in matched tissues from the same animal are connected by dotted lines. In addition to the individual values, medians with interquartiles are shown.