Fig. 3.

Apical Na⁺ current and Na⁺ fluxes in non-CF and CF epithelia. (A) Amiloride-sensitive current in epithelia with a permeabilized basolateral membrane and an apical-to-basolateral Na⁺ concentration gradient. n = 11 non-CF and 8 CF epithelia, all from different donors. (B) Open-circuit Na⁺ unidirectional and net Na⁺ flux rates determined isotopically under basal conditions and after addition of 100 μM amiloride apically. J^Na_ap-bl indicates Na⁺ flux from the apical to the basolateral surface, J^Na_bl-ap indicates flux in the opposite direction, and J^Na_net indicates net flux. n = 9 non-CF and 9 CF donors with one pair of epithelia from each donor. In matched epithelia, Vt was −20 ± 5 mV for non-CF and −24 ± 4 mV for CF epithelia; Isc was 44 ± 7 μA·cm⁻² for non-CF and 47 ± 8 μA·cm⁻² for CF; Gt was 2.2 ± 0.3 mS·cm⁻² for non-CF and 1.8 ± 0.2 mS·cm⁻² for CF.