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

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.

Keyword

Guinea-pig ileum; Outward K+ currents; Sodium nitroprusside, cGMP; TEA; 4-AP; ODQ

MeSH Terms

4-Aminopyridine
Apamin
Egtazic Acid
Glyburide
Guanylate Cyclase
Humans
Ileum*
Muscle, Smooth*
Myocytes, Smooth Muscle*
Nitric Oxide*
Nitroprusside
Potassium Channels, Calcium-Activated
Potassium*
Relaxation
S-Nitroso-N-Acetylpenicillamine
Tea
Tetraethylammonium
Tissue Donors
4-Aminopyridine
Apamin
Egtazic Acid
Glyburide
Guanylate Cyclase
Nitric Oxide
Nitroprusside
Potassium
Potassium Channels, Calcium-Activated
S-Nitroso-N-Acetylpenicillamine
Tea
Tetraethylammonium
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