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Identification of Calcium‐Activated Potassium Channels in Cultured Equine Sweat Gland Epithelial Cells
Author(s) -
Huang Yu,
Ko WingHung,
Chung YiuWa,
Wong P. Y. D.
Publication year - 1999
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1111/j.1469-445x.1999.01801.x
Subject(s) - iberiotoxin , chemistry , depolarization , tetraethylammonium , biophysics , membrane potential , conductance , repolarization , patch clamp , potassium channel , population , endocrinology , medicine , electrophysiology , potassium , biochemistry , biology , receptor , mathematics , environmental health , organic chemistry , combinatorics
SUMMARY The patch‐clamp recording technique was used to examine the properties of the K + channels in cultured equine sweat gland epithelial cells. With symmetric K + solutions (140 mM), a single population of K + channels was identified with a slope conductance of 187 pS and a reversal potential of around 0 mV. The channel was selective for K + over Na + . Channel activity was increased by membrane depolarization. A 10‐fold increase in [Ca 2+ ] i produced an approximate 60 mV negative shift in the open state probability ( P open )‐voltage curve. Externally applied tetraethylammonium ions (TEA + ) caused a rapid and flickery block of the channel and reduced the unitary current amplitude. TEA + bound to the blocking site with stoichiometry of 1:1 and with a dissociation constant ( K d ) of 186 ± 27 μM at +40 mV. A weak voltage dependence of K d was observed. Iberiotoxin (100 nM) reduced P open but had no effect on single‐channel conductance. Neither glibenclamide (10 μM) nor intracellular adenosine 5′‐triphosphate (ATP, 1 mM) altered channel activity. In addition, ATP, when applied extracellularly, transiently activated the channel by increasing P open . Channel activity was low around the resting membrane potential in the intact epithelia, indicating that these channels might not contribute to the resting K + conductance. However, the channel could be activated in a regulated manner. The K + channels may play a role in transepithelial fluid secretion in sweat gland.