Role of calcium mobilization in sodium nitroprusside-induced increase of calcium-activated potassium currents in gastric antral circular myocytes of guinea pig.
OBJECTIVE
To investigate the role of calcium mobilization in the calcium-activated potassium currents [IK(Ca)] increased by sodium nitroprusside (SNP), a nitric oxide (NO) donor, in gastric antral circular myocytes of the guinea pig.


METHODS
A perforated patch-clamp technique was used, and the myocytes were isolated by collagenase.


RESULTS
SNP 100 mol/L significantly increased IK(Ca), and enhanced the spontaneous transient outward currents (STOC). SNP-induced increase of IK(Ca) was not blocked by extracellular calcium-free solution (containing egtazic acid 10 micromol/L and nicardipine 5 micromol/L, an L-type calcium channel blocker. And SNP 100 micromol/L suppressed the L-type calcium currents (ICa). SNP-induced increase of STOC was inhibited by heparin 3 g/L, a potent inhibitor of inositol triphosphate receptor (InsP3R). However, ryanodine 10 micromol/L, an inhibitor of calcium-induced calcium release (CICR), did not inhibit the effect of SNP-induced increase of STOC. Methylene blue (1 micromol/L), an inhibitor of soluble guanylate cyclase, also inhibited such an effect.


CONCLUSIONS
The increase of IK(Ca) caused by SNP may be mediated by cGMP via IP3-sensitive calcium pools, however, extracellular Ca2+ may not be involved in the process.
Yu
Yong-Chun
YC
Research Laboratory of Digestive Physiology, College of Medicine, Yanbian University, Yanji 133000, China.
Guo
Hui-Shu
HS
Li
Ying
Y
Piao
Lin
L
Li
Lin
L
Li
Zai-Liu
ZL
Xu
Wen-Xie
WX
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels; D002469:Cell Separation; D005260:Female; D006168:Guinea Pigs; D006493:Heparin / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008297:Male; D032342:Muscle Cells / Q000187:drug effects* / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology; D009529:Nicardipine / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology*; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D011706:Pyloric Antrum / Q000166:cytology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000037:antagonists & inhibitors
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D020030:Nitric Oxide Donors; D024681:Potassium Channels, Calcium-Activated; D018160:Receptors, Cytoplasmic and Nuclear; D009599:Nitroprusside; D006493:Heparin; D009529:Nicardipine