Modulation of outward potassium currents by nitric oxide in longitudinal smooth muscle cells of guinea-pig ileum.
- Author:
Seong Chun KWON
1
;
Se Joong RIM
;
Bok Soon KANG
Author Information
1. Department of Physiology, Yonsei University College of Medicine, Seoul 120-752, Korea.
- Publication Type:Original Article
- Keywords:
Guinea-pig ileum;
Outward K+ currents;
Sodium nitroprusside, cGMP;
TEA;
4-AP;
ODQ
- MeSH:
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
- From:The Korean Journal of Physiology and Pharmacology
1998;2(2):225-232
- CountryRepublic of Korea
- Language:English
-
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.
