Korean J Physiol Pharmacol.
1998 Apr;2(2):225-232.
Modulation of outward potassium currents by nitric oxide in longitudinal smooth muscle cells of guinea-pig ileum
- Affiliations
-
- 1Department of Physiology, Yonsei University College of Medicine, Seoul 120-752, Korea.
- 2Department of Internal Medicine, Yonsei University College of Medicine, Seoul 120-752, Korea.
Abstract
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To investigate the possible involvement of outward potassium (K+)
currents in nitric oxide-induced relaxation in intestinal smooth
muscle, we used whole-cell patch clamp technique in freshly dispersed
guinea-pig ileum longitudinal smooth muscle cells. When cells were held
at -60 mV and depolarized from - 40 mV to + 50 mV in 10 mV increments,
sustained outward K+ currents were evoked. The outward K+ currents were
markedly increased by the addition of 10 muM sodium nitroprusside
(SNP). 10 muM S-nitroso-N-acetylpenicillamine (SNAP) and 1 mM
8-Bromo-cyclic GMP (8-Br-cGMP) also showed a similar effect to that of
SNP. 1 mM tetraethylammonium (TEA) significantly reduced
depolarization-activated outward K+ currents. SNP-enhanced outward K+
currents were blocked by the application of TEA. High EGTA containing
pipette solution (10 mM) reduced the control currents and also
inhibited the SNP-enhanced outward K+ currents. 5 mM 4-aminopyridine
(4-AP) significantly reduced the control currents but showed no effect
on SNP-enhanced outward K+ currents. 0.3 muM apamin and 10 muM
glibenclamide showed no effect on SNP-enhanced outward K+ currents. 1
muM 1H-(1,2,4)oxadiazolo (4,3-a)quinoxaline-1-one (ODQ), a specific
inhibitor of soluble guanylate cyclase, significantly blocked
SNP-enhanced K+ currents. We conclude that NO donors activate the
Ca2+-activated K+ channels in guinea-pig ileal smooth muscle via
activation of guanylate cyclase.