ISSN:
1432-2013
Keywords:
Mammary epithelial cells
;
Patch clamp
;
K+ channel
;
Ca2+ activation
;
Na+ block
;
A23187
;
Inward rectification
;
Epidermal growth factor
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract The properties of Ca2+-activated K+ channels in mouse mammary epithelial cells in primary culture were studied by the patch-clamp technique. In cell-attached patches, spontaneous channel openings were sometimes observed; the slope conductance of the currents was about served; the slope conductance of the currents was about 12 pS at negative membrane potentials with a physiological solution (152 mM Na+, 5.4 mM K+) in the pipette. External application of A23187, a calcium ionophore, activated this channel. In excised inside-out patches, the channel was activated by increasing the internal Ca2+ concentration (10−7 to 10−6 M). No voltage dependence of the channel activity was observed. Internal Na+ blocked the outward K+ current in a voltage dependent manner and this block led to the non-linear I–V relationship at positive membrane potentials. The channel was blocked by internal Ba2+ (0.1 mM) and tetracthylammonium (TEA+, 20–50 mM). Ba2+ reduced the open probability but not the single channel conductance, whereas TEA+ reduced the single channel conductance. The single channel conductance of this channel, measured from the inward current with a high-K+ solution (150 mM K+) in the pipette, was large (about 40 pS), and showed inward rectification. These results suggest that this channel is different from the usual small conductance Ca2+-activated K+ channels observed in many other cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00580952
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