Effect of nitric oxide on calcium-activated potassium channels in colonic smooth muscle of rabbits

Gang Lu, Bruno Mazet, Michael G. Sarr, Joseph H. Szurszewski

Research output: Contribution to journalArticle

Abstract

Nitric oxide (NO) hyperpolarizes intestinal smooth muscle cells. This study was designed to determine the mechanism whereby NO activates K(Ca) channels of circular smooth muscle of the rabbit colon. Transmural biopsies of the rabbit colon were stained for NADPH-diaphorase. Freshly dispersed circular smooth muscle cells were studied in the whole cell configuration, as well as in on-cell and excised inside-out patch recording configurations, while K(Ca) current and the activity of Kca channels, respectively, were monitored. NADPH-diaphorase-positive nerve fibers were found in both muscle layers. NO (1%) increased whole cell net outward current by 79% and hyperpolarized resting membrane voltage from -59 to -73 mV (n = 8 cells, P < 0.01). In the on-cell patch recording configuration, NO (0.5% or 1%) in the bath increased NP(o) of K(Ca) channels; charybdotoxin (125 nM) in the pipette solution blocked this effect. In the excised inside-out patch recording configuration, NO (1%) had no effect on NP(o) of K(Ca), channels. In the on- cell patch recording configuration, methylene blue (1 μM) or cystamine (5 mM) in the bath solution decreased the effect of NO (1%) on NP(o) of K(Ca) channels. NP(o) was increased by 8-bromo-cGMP (8-BrcGMP; 1 mM), a cGMP analog, and zaprinast (100 μM), an inhibitor of cGMP phosphodiesterase. These data suggest that NO increased whole cell outward K+ current by activating K(Ca) channels through a cGMP pathway.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume274
Issue number5 37-5
StatePublished - May 1998

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Calcium-Activated Potassium Channels
Smooth Muscle
Nitric Oxide
Rabbits
NADPH Dehydrogenase
Baths
Smooth Muscle Myocytes
Colon
Cystamine
Charybdotoxin
Phosphodiesterase Inhibitors
Methylene Blue
Nerve Fibers
Biopsy
Muscles
Membranes

Keywords

  • Dispersed smooth muscle cells
  • Guanosine 3',5'-cyclic monophosphate
  • NADPH diaphorase

ASJC Scopus subject areas

  • Physiology
  • Gastroenterology

Cite this

Effect of nitric oxide on calcium-activated potassium channels in colonic smooth muscle of rabbits. / Lu, Gang; Mazet, Bruno; Sarr, Michael G.; Szurszewski, Joseph H.

In: American Journal of Physiology - Gastrointestinal and Liver Physiology, Vol. 274, No. 5 37-5, 05.1998.

Research output: Contribution to journalArticle

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abstract = "Nitric oxide (NO) hyperpolarizes intestinal smooth muscle cells. This study was designed to determine the mechanism whereby NO activates K(Ca) channels of circular smooth muscle of the rabbit colon. Transmural biopsies of the rabbit colon were stained for NADPH-diaphorase. Freshly dispersed circular smooth muscle cells were studied in the whole cell configuration, as well as in on-cell and excised inside-out patch recording configurations, while K(Ca) current and the activity of Kca channels, respectively, were monitored. NADPH-diaphorase-positive nerve fibers were found in both muscle layers. NO (1{\%}) increased whole cell net outward current by 79{\%} and hyperpolarized resting membrane voltage from -59 to -73 mV (n = 8 cells, P < 0.01). In the on-cell patch recording configuration, NO (0.5{\%} or 1{\%}) in the bath increased NP(o) of K(Ca) channels; charybdotoxin (125 nM) in the pipette solution blocked this effect. In the excised inside-out patch recording configuration, NO (1{\%}) had no effect on NP(o) of K(Ca), channels. In the on- cell patch recording configuration, methylene blue (1 μM) or cystamine (5 mM) in the bath solution decreased the effect of NO (1{\%}) on NP(o) of K(Ca) channels. NP(o) was increased by 8-bromo-cGMP (8-BrcGMP; 1 mM), a cGMP analog, and zaprinast (100 μM), an inhibitor of cGMP phosphodiesterase. These data suggest that NO increased whole cell outward K+ current by activating K(Ca) channels through a cGMP pathway.",
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