cAMP regulation of Cl− and HCO 3 − secretion across rat fetal distal lung epithelial cells

Abstract

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 basal I 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[Formula: see text] secretion, blocked the remaining I sc. Forskolin addition evoked currents of similar fractional magnitudes in symmetrical Cl−- or HCO[Formula: see text]-free solutions; however, no response was seen using HCO[Formula: see text]- and Cl−-free solutions. The forskolin-stimulated I sc was inhibited by glibenclamide but not apical DIDS. Glibenclamide also blocked forskolin-induced I sc across monolayers having nystatin-permeablized basolateral membranes. Immunolocalization studies were consistent with the expression of cystic fibrosis transmembrane conductance regulator (CFTR) protein in FDLE cells. In aggregate, these findings indicate the presence of cAMP-activated Cl− and HCO[Formula: see text] secretion across rat FDLE cells mediated via CFTR.