FIGURE 4.

Effect of shaking on the magnitude of ENaC activity, measured as amiloride-sensitive Isc_eq. mCD cell monolayers were incubated with or without shaking for 24 h at the indicated frequency. Isc_eq was measured immediately after termination of shaking and normalized relative to Isc_eq of unshaken monolayers. The absolute value for the control short-circuit current I_sc is ∼10 μA/cm², with a standard deviation of ∼1 μA/cm². Number of unshaken control monolayers = 20; number of shaken monolayers = 16 at each frequency. Asterisks indicate a p < 0.01 compared to unshaken monolayers. The effect of shaking on ENaC current is already maximal at the lowest frequency tested. The same experiment was performed with monolayers exhibiting higher I_sc, ∼50 μA/cm², with the same results (data not shown).