EXPRESSION OF CFTR AND A CAMP-STIMULATED CHLORIDE SECRETORY CURRENT IN CULTURED HUMAN FETAL ALVEOLAR EPITHELIAL-CELLS

Citation
Pb. Mccray et al., EXPRESSION OF CFTR AND A CAMP-STIMULATED CHLORIDE SECRETORY CURRENT IN CULTURED HUMAN FETAL ALVEOLAR EPITHELIAL-CELLS, American journal of respiratory cell and molecular biology, 9(6), 1993, pp. 578-585
Citations number
43
Categorie Soggetti
Cytology & Histology",Biology,"Respiratory System
ISSN journal
10441549
Volume
9
Issue
6
Year of publication
1993
Pages
578 - 585
Database
ISI
SICI code
1044-1549(1993)9:6<578:EOCAAC>2.0.ZU;2-W
Abstract
During development the fetal lung secretes fluid that is osmotically l inked to chloride (Cl-) transport. One possible pathway for Cl- secret ion across the fetal pulmonary epithelium is through the cystic fibros is transmembrane conductance regulator (CFTR). CFTR is expressed in ep ithelia and functions as a Cl- channel regulated by cyclic adenosine m onophosphate (cAMP)-dependent protein kinase and intracellular ATP. Pr evious studies have shown that CFTR mRNA is expressed throughout the h uman fetal pulmonary epithelium and CFTR protein can be immunoprecipit ated from human fetal lung homogenates. In cultured fetal lung tissue explants, CFTR mRNA was localized to alveolar epithelial cells. To tes t the hypothesis that fetal alveolar epithelial cells express function al CFTR, we immunolocalized CFTR in human fetal lung and looked for ev idence of Cl- secretion in cultured alveolar epithelial cell monolayer s. Monoclonal anti-CFTR antibodies localized CFTR in cultured lung exp lants to the epithelial cells, predominantly at the apical surface. Bi oelectric properties of cultured monolayers of midgestation fetal alve olar epithelial cells were measured in modified Ussing chambers. In un stimulated monolayers, transepithelial electrical potential difference (Psi(t))= -1.1 +/- 0.1 mV, transepithelial resistance (R(t)) = 768 +/ - 58 Omega.cm(2), and short-circuit current (I-sc) = 1.9 +/- 0.2 mu A/ cm(2) (mean +/- SE, n = 17). Addition of amiloride to the apical surfa ce significantly decreased basal I-sc. Apical diphenylamine-2-carboxyl ate (DPC), a Cl- channel inhibitor, caused no significant change in ba sal I-sc. In the presence of apical amiloride, isoproterenol significa ntly increased I-sc a response that was inhibited by apical DPC and su bmucosal bumetanide. The cAMP agonists forskolin and IBMX also stimula ted I-sc. These results suggest that human fetal alveolar epithelial c ells express CFTR, which mediates cAMP-stimulated transepithelial Cl- secretion.