Nicotine inhibits large conductance Ca(2+)-activated K(+) channels and the NO/-cGMP signaling pathway in cultured human endothelial cells.
OBJECTIVE
The effects of nicotine on endothelium-dependent vasorelaxation mediated by nitric oxide (NO) are controversial. Since endothelial NO synthesis has been shown to depend on the activity of large conductance Ca(2 + )-activated K(+) channels (BK(Ca)), the present study investigated whether nicotine alters BK(Ca) single channel activity induced by the K(+) channel opener NS1619, and to examine a possible interaction with the endothelial NO generation.


METHODS
The patch-clamp technique was used to examine the BK(Ca) activity. NO production was measured indirectly using a [(3)H]-cGMP-radioimmunoassay. All experiments were performed using cultured endothelial cells derived from human umbilical cord veins.


RESULTS
The BK(Ca) opener NS1619 (10 micromol/l) significantly increased the BK(Ca) open-state probability (NPo) from 0.011+/-0.007 (control) to 0.052+/-0.019. Co-perfusion with nicotine (1 micromol/l) significantly decreased NS1619 induced NPo (n = 14, p < 0.05). Intracellular cGMP levels were significantly increased, if cells were stimulated with NS1619 (+ 225%; n = 10, p < 0.05), which was blocked by Nicotine (1 micromol/l).


CONCLUSIONS
The results of the present study demonstrate that BK(Ca) activation by NS1619 plays an important role in the regulation of the NO-/cGMP-signaling-pathway. Endothelial dysfunction caused by nicotine may be connected with a decrease in BK(Ca)-activity.
Kuhlmann
Christoph Rüdiger Wolfram
CR
Department of Cardiology and Angiology, Justus-Liebig-University of Giessen, Klinikstrasse 36, Giessen 35392, Germany.
Trümper
Jan Rasmus Friedrich Carl
JR
Tillmanns
Harald
H
Alexander Schaefer
Christian
C
Erdogan
Ali
A
D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology; D006152:Cyclic GMP; D004594:Electrophysiology; D042783:Endothelial Cells / Q000187:drug effects* / Q000502:physiology; D016232:Endothelins / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D009538:Nicotine / Q000009:adverse effects / Q000494:pharmacology*; D009569:Nitric Oxide; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*
D015220:Calcium Channels; D016232:Endothelins; D015221:Potassium Channels; D009569:Nitric Oxide; D009538:Nicotine; D006152:Cyclic GMP