Effects of nitroprusside, 3-morpholino-sydnonimine, and spermine on calcium-sensitive potassium currents in gastric antral circular myocytes of guinea pig.
OBJECTIVE
To determine the effect of nitric oxide (NO) on calcium-activated potassium currents in antral circular myocytes of the guinea pig stomach.


METHODS
The whole-cell patch-clamp techniques were used, and the cells were isolated by collagenase. Sodium nitroprusside (SNP), spermine, and 3-morpholino-sydnonimine (SIN-1) were used as nitric oxide donors.


RESULTS
Outward potassium currents were remarkably inhibited by tetraethylammonium (TEA) 1 mmol.L-1. Charybdotoxin 200 nmol.L-1, a specific inhibitor of KCa channel, also greatly inhibited IK(Ca). NO donors remarkably increased IK(Ca) in guinea pig gastric antral circular myocytes with perforated patch-clamp techniques but not conventional whole-cell patch-clamp techniques. Spermine 100 mumol.L-1 increased IK(Ca) by 14% +/- 10% (at 60 mV, P < 0.01), SIN-1 200 mumol.L-1 increased IK(Ca) by 19% +/- 14% (at 60 mV, P < 0.01), and SNP 100 mumol.L-1 increased IK(Ca) by 24% +/- 13% (at 60 mV, P < 0.01) respectively. SIN-1- and SNP-induced increase of IK(Ca) was blocked by methylene blue 1 mumol.L-1.


CONCLUSIONS
NO increases calcium-activated potassium currents in gastric antral circular myocytes of guinea pig, and the effect of NO on IK(Ca) may be mediated by cyclic GMP.
Li
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Research Laboratory of Gastrointestinal Physiology, College of Medicine, Yanbian University, Yanji 133000, China.
Xu
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Li
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D000818:Animals; D002469:Cell Separation; D005260:Female; D006168:Guinea Pigs; D008297:Male; D008981:Molsidomine / Q000031:analogs & derivatives / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000166:cytology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects*; D011706:Pyloric Antrum / Q000166:cytology; D013096:Spermine / Q000494:pharmacology*
D020030:Nitric Oxide Donors; D015221:Potassium Channels; D009599:Nitroprusside; D013096:Spermine; C002385:linsidomine; D008981:Molsidomine