Calcium-activated potassium channels in cultured human endothelial cells are not directly modulated by nitric oxide.
Nitric oxide has been proposed to directly activated large conductance Ca(2+)-dependent K+ channels (BKCa) [Bolotina V.M., Najibi S., Palacino J.J., Pagano P.J., Cohen R.A. Nitric oxide directly activates calcium-dependent potassium channels in vascular smooth muscle. Nature 1994; 368: 850-853]. The nitric oxide (NO) donor S-nitrosocysteine (SNOC) was used to evaluate a possible direct modulation of BKCa by NO in EAhy926 (EA cells), a cultured human umbilical vein derived endothelial cell line, using the whole-cell, cell-attached and inside-out configuration of the patch-clamp technique, together with simultaneous amperometric measurement of NO and the concentration of free intracellular calcium [Ca2+]i. BKCa channels with a large conductance of approximately 190 pS, voltage-dependent activation and a reversal potential close to -80 mV have been identified in EA cells. Exposure of EA cells in the experimental chamber to 1 mM SNOC delivered approximately 5 microM NO, as recorded by an amperometric probe in situ. SNOC produced a modest increases in [Ca2+]i that was insufficient to activate BKCa channels. NO alone neither activated BKCa channels directly nor modulated preactivated BKCa channels in EA cells. These results do not support a direct modulatory effect of NO on large conductance BKCa channels in cultured endothelial cells.
Haburcák
M
M
Laboratorium voor Fysiologie, Campus Gasthuisberg, Leuven, Belgium.
Wei
L
L
Viana
F
F
Prenen
J
J
Droogmans
G
G
Nilius
B
B
D002478:Cells, Cultured; D003545:Cysteine / Q000031:analogs & derivatives / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism*; D006801:Humans; D051036:Large-Conductance Calcium-Activated Potassium Channels; D009126:Muscle Relaxation; D009569:Nitric Oxide / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D026403:S-Nitrosothiols
D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D026403:S-Nitrosothiols; D009569:Nitric Oxide; C021315:S-nitrosocysteine; D003545:Cysteine