ISSN:
1432-2013
Keywords:
Key words Anion permeation
;
CFTR
;
Cystic fibrosis
;
Pore size
;
Tight junction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract Anion selectivity of the cystic fibrosis conductance transmembrane conductance regulator (CFTR) and other channels and parallel pathways expressed endogenously in apical membranes of polarized Calu-3 epithelial monolayers was studied under control conditions and during cAMP stimulation. Basolateral membranes were eliminated using alpha-toxin. The cAMP-stimulated, gradient-driven currents had the sequence Br≥Cl≥NO3〉SCN〉 I≥F〉formate〉HCO3〉acetate〉propionate=butyrate=ATP= PPi=PO4=SO4=0. Selectivity of parallel cAMP-independent pathway(s) was Br〉Cl=SCN=NO3〉I〉formate=F 〉HCO3〉acetate〉propionate. SCN, I, F or formate blocked cAMP-stimulated, but not control, Cl currents. Anions 〉0.53 nm in diameter were impermeant, suggesting that the apical CFTR channel has a limiting diameter of 0.53 nm. The selectivity, blocking patterns and pore size of the cAMP-stimulated conductance pathway were very similar to those in previous reports in which CFTR was heterologously expressed in non-epithelial cells. Thus, CFTR appears to be the major apical anion conductance pathway in Calu-3 cells, and its conduction properties are independent of the expression system. CFTR in Calu-3 cells also conducts physiologically relevant anions, but not ATP, PO4 or SO4. A pathway parallel (probably a tight junction) showed a different selectivity than CFTR.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004240050850
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