ISSN:
1432-2013
Keywords:
Apical cell membrane
;
K+ channel
;
Patch-clamp
;
Gallbaladder
;
Ca2+ activation
;
Voltage activation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The presence of Ca2+- and voltage-activated K+ channels was directly demonstrated in the apical cell membrane of gallbladder epithelium by patch-clamp single-channel current recording. In K+-depolarized epithelial cells, negative pipette potentials induced outward current steps when the patch-pipette was filled with Na+-rich solution and these current steps were not affected by the presence or absence of Cl−. When K+-rich solution was in the pipette and K+-depolarized cells were examined, the current-voltage relations were linear with a single-channel conductance of 140 pS and polarity was reversed at 0 mV. In excised inside-out membrane patches, raising the free Ca2+ concentration of the medium facing the inner side of the membrane from 10−7 to 10−6 M evoked a marked increase in open state probability of the channels without affecting the elementary current steps. This suggests that intracellular Ca2+ as a second messenger plays a crucial role in the regulatory mechanism of the membrane potential by modulating the high-conductance apical K+ channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00584021
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