Figure 5. The selectivity properties of the UTP-activated, apamin-sensitive apical membrane conductance.

A, current–voltage relationship of monolayers maintained in the presence of 20 nm oestradiol-17β for 4 days and bathed with an apical solution containing 15 mm[K⁺]. The reversal potential was −52 ± 2 mV (n = 4). The current–voltage relationship exhibited slight inward rectification as revealed by attempting a linear fit over the entire range of values. A line connecting points between −40 mV and +40 mV failed to intersect data points between −60 mV and −100 mV, which deviated below the line by more than their s.e.m. values. B, effects of extracellular [K⁺] on reversal potential of the apamin-sensitive apical current (n = 4 at 15 mm[K⁺]; n = 6 at 40 and 100 mm[K⁺]).