Reconstitution of Single Potassium Channels from Bovine Gall bladder Epithelium*
1998
The study of molecular transport across gall-bladder epithe lium may contribute to our understanding of the pathophys iology of gall-bladder disease. The aim of this study was to reconstitute and characterize single potassium ion channels in bovine gall-bladder epithelial mucosa - both apical and basolateral aspects. Standard subcellular fractionation tech niques were used to form either apical or basolateral closed membrane vesicles from the mucosal epithelium offresh gall bladders from healthy young adult cattle. Vesicular ion channels were incorporated into voltage-clamped planar lipid bilayers under known ionic conditions and their con ductances, reversal potentials, and voltages were character ized. Low-conductancevoltage-insensitive apical membrane vesicle channels of at least four conductance levels were found (mean ± SD): 12 ± 4 pS, n = 10; 40 ± 12 pS, n = 4; 273 ± 31 pS, n =3; and 151 ± 24 pS, n =5. Conductances of potassium ion channels in basolateral membrane vesicles were in the range 9 - 450 pS, and these channels included high-conductance calcium-activated potassium-ion chan nels 'K(Ca)' which were voltage- and calcium-dependent.
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