A Chloride Conductance Evoked by Hypotonic Shock in Epithelial Cells
Single channel recordings have shown that airway epithelial cells possess apical rectifying Cl- channels whose activity is regulated by the cAMP pathway. Several reports (Frizzell et al., 1986; Welsh and Liedtke 1986; Schoumacher et al., 1987; Li et al., 1988) indicate an altered regulation of these chloride channels as the possible functional defect causing cystic fibrosis (CF). We asked whether the defective regulation of Cl- channels in CF can also be detected in the whole-cell configuration of the patch-clamp technique. This approach, which allows to record macroscopic membrane currents, gives a more representative view of the whole cell membrane conductance. The possible existence of different types of Cl- currents can be more easily detected. Furthermore, in polarized cells, the whole-cell technique allows to record currents flowing through the basolateral membrane which is not accessible to the patch pipette. Recent reports using the whole-cell approach have shown that colonic carcinoma T84 cells (Worrell et al., 1989) and primary culture respiratory cells (Schoppa et al., 1989; McCann et al., 1989) have a Cl- conductance characterized by inactivation at positive membrane potentials. Two of these papers (Worrell et al., 1989; McCann et al., 1989) report that the inactivating Cl- current is sensitive to cell volume changes.
KeywordsAlbumin Cytosol Mannitol Lution EGTA
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