cAMP regulation of Cl(-) and HCO(-)(3) secretion across rat fetal distal lung epithelial cells.

We isolated and cultured fetal distal lung epithelial (FDLE) cells from 17- to 19-day rat fetuses and assayed for anion secretion in Ussing chambers. With symmetrical Ringer solutions, basal short-circuit currents (I sc) and transepithelial resistances were 7.9 ± 0.5 μA/cm2 and 1,018 ± 73 Ω · cm2, respectively (means ± SE;n = 12). Apical amiloride (10 μM) inhibited basalI sc by ∼50%. Subsequent addition of forskolin (10 μM) increased I sc from 3.9 ± 0.63 μA/cm2 to 7.51 ± 0.2 μA/cm2(n = 12). Basolateral bumetanide (100 μM) decreased forskolin-stimulated I sc from 7.51 ± 0.2 μA/cm2 to 5.62 ± 0.53, whereas basolateral 4,4′-dinitrostilbene-2,2′-disulfonate (5 mM), an inhibitor of HCO 3 − secretion, blocked the remainingI sc. Forskolin addition evoked currents of similar fractional magnitudes in symmetrical Cl−- or HCO 3 − -free solutions; however, no response was seen using HCO 3 − - and Cl−-free solutions. The forskolin-stimulated I sc was inhibited by glibenclamide but not apical DIDS. Glibenclamide also bl...