Figure 7.

The effects of decreasing apical extracellular K⁺ from 5 to 0 mM (n = 8). The arrows indicate the time points when a new bath solution was applied to the bath or when the agonist ATP was added to the bath solution. (A) Continuous recording of the I_SC as a function of time before and after the apical and basolateral change of normal Krebs solution to low K⁺ Krebs solution. The upward deflections are current responses to voltage pulses of 1 mV, 1 ms in duration, to measure TER. The red line is the control regression line calculated between the last three I_SC measurements of the control period at the beginning and the last three I_SC measurements of the control period at the end of the experiment. (B) The mean I_SC as a function of time before and after the apical and basolateral change of normal Krebs solution to low K⁺ Krebs solution. The ordinate shows the measured value of the I_SC (in µA/cm²), and the red line is the control regression line, as in A. (C) TER as a function of time before and after the apical and basolateral change of normal Krebs solution to low K⁺ Krebs solution. The ordinate shows the measured value of TER (in ohm·cm²), and the red line is the control regression line, as in A.