Figure 3. Bile acids regulate ENaC currents in the distal colon.

Colons isolated from mice on a normal salt diet (A), or after 9-10 days on a low Na⁺ diet (C, E) were mounted in an Ussing chamber for I_SC measurements. After tissue equilibration, baseline currents were measured for at least 5 minutes before the addition of the first compound. Basal I_SC averaged 76 (15) μA/cm² for colons from mice on a normal salt diet, and 117 (43) μA/cm² for colons from mice on a low salt diet. 1 mM t-CA, 1 mM t-HDCA, or 100 μM amiloride were added to the apical bath as indicated. B, D, F, The effect of each compound on I_SC (ΔI_SC) was determined by measurements taken 4 min apart: 30 s before and 3.5 min after compound addition. The value of ΔI_SC was then normalized to the baseline current in the same recording to account for inter-animal variability in starting I_SC. t-CA- and t-HDCA-induced ΔI_SC in the absence or presence of amiloride were compared by Student’s t test. Individual experiments (blue; n = 3 colons from mice fed a low salt diet for t-CA with amiloride pretreatment; n = 4 colons for other groups) and summary statistics (mean (SD)) are shown.