RECONSTITUTION OF SINGLE POTASSIUM CHANNELS FROM BOVINE GALLBLADDER EPITHELIUM

The study of molecular transport across gall-bladder epithelium may co ntribute to our understanding of the pathophysiology of gall-bladder d isease, The aim of this study was to reconstitute and characterize sin gle potassium ion channels in bovine gall-bladder epithelial mucosa - both apical and basolateral aspects. Standard subcellular fractionatio n techniques were used to form either apical or basolateral closed-mem brane vesicles from the mucosal epithelium of fresh gall bladders from healthy young adult cattle, Vesicular ion channels were incorporated into voltage-clamped planar lipid bilayers under known ionic condition s and their conductances, reversal potentials, and voltages were chara cterized. Low-conductance voltage-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 1 51 +/- 24 pS, n = 5, Conductances of potassium ion channels in basolat eral membrane vesicles were in the range 9 - 450 pS, and these channel s included high-conductance calcium-activated potassium-ion channels ' K(Ca)' which were voltage- and calcium-dependent.