ISSN:
1432-2013
Keywords:
Human respiratory epithelial cells
;
Cell fusion
;
Ca2+-regulated Cl− conductance
;
cAMP-regulated Cl− conductance
;
Halide anion selectivities
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract With the aim of further elucidating the role of the epithelial Cl− conductance and its defect in cystic fibrosis (CF) patients we studied the properties and regulation of the Cl− conductance in primary cultures of human nasal polyp epithelia. To facilitate microelectrode punctures and to gain access to the cytoplasmic compartment for injection of antibodies, we prepared giant cells using a polyethylene-glycol fusion technique. The membrane potential (V m) and resistance (R m) and their responses to ionic substitutions in the bath were measured under control conditions and in the presence of different secretagogues. In non-CF cells V m averaged −12.5 mV (SD±6.6 mV, n=69) and was independent of time after fusion, while R m dropped from 12.4±7.3 MΩ (n=51) to 3.5±5.5 MΩ (n=24) in the 2nd week after fusion. The low V m values reflected a vanishing K+ conductance in the presence of a dominating Cl− conductance that increased with time. In young cells, a Cl− conductance prevailed which could be stimulated by application of the Ca2+ ionophore, A23187, or of carbachol. As determined in CF cells, it had an outwardly rectifying current/voltage (i/V) relationship and exhibited the selectivity sequence I−〉Br−〉Cl−〉F−〉 isethionate (ISE−) both in V m and R m measurements. With increasing age after fusion, a Cl− conductance prevailed in non-CF cells which could be stimulated by cyclic adenosine monophosphate (cAMP) or forskolin and which was downregulated by A23187. It had a linear i/V relationship and exhibited the selectivity sequence Br−〉Cl−〉I−〉F−〉 ISE− if determined from V m measurements, but a sequence of Cl−〉Br−〉F− =ISE−〉I− if determined from R m measurements. This points to multiple-ion pore behaviour of the respective Cl− channel. In agreement with observations described in the following publication, the results suggest that the cAMP-regulated Cl− conductance corresponds to the CF-gene product while the molecular nature of the Ca2+-regulated Cl conductance is not yet known.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374656
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