Apical K+ Channels in Frog Skin: A Pathway for K+ Excretion
Since several decennia, the transport of Na+ across the epithelium of frog skin has been the subject of numerous studies (Lindemann and Voûte 1976). Particularly, special interest was given to the mechanisms involved in uptake of Na+ across the apical barrier, which was found to be the rate limiting step in Na+ translocation from the mucosal to serosal compartment (Biber and Curran 1970). It was generally accepted that the apical membranes were mainly permeable for Na+ and did not display a measurable permeability for K+ (Koefoed-Johnsen and Ussing 1958). Recently, we found that the apical cell membranes of the skin of frog species Rana temporaria have also a significant K+ conductance (Zeiske and Van Driessche 1979). However, the permeability for K+ varied enormously among frogs. This might have been the reason for the ignorance about this pathway during several decades of investigations of the frog skin epithelium.
KeywordsApical Membrane Corner Frequency Local Electrical Field Noise Analysis Blockable Current
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