Nitric oxide activation of a potassium channel (BK_(Ca)) in feline lower esophageal sphincter

查看全文 作　　者：Marie-Claude L'[1,2]Heureux;Ahmad [1,3]Muinuddin;Herbert Y [1,3]Gaisano;Nicholas E [1,3]Diamant

机构地区：[1]Department of Physiology,University of Toronto;[2]Ahmad Muinuddin,Nicholas E Diamant,Toronto Western Research Institute,University Health Network;[3]Department of Medicine,University of Toronto

出　　处：《World Journal of Gastroenterology》索引2010年第16卷第46期,共9页

基　　金：Supported by A Postgraduate Fellowship Award to L'Heureux MC from the Department of Medicine,University of Toronto;a doctoral research studentship and an Operating Grant from the Canadian Institutes of Health Research(Gaisano HY and Diamant NE) 摘　　要：AIM:To assess the effect of nitric oxide (NO) on the large conductance potassium channel (BKCa) in isolated circular (CM) and sling (SM) muscle cells and muscle strips from the cat lower esophageal sphincter (LES) to determine its regulation of resting tone and relaxation.METHODS:Freshly enzymatically-digested and isolated circular smooth muscle cells were prepared from each LES region.To study outward K + currents,the perforated patch clamp technique was employed.To assess LES resting tone and relaxation,muscle strips were mounted in perfused organ baths.RESULTS:(1) Electrophysiological recordings from isolated cells:(a) CM was more depolarized than SM (-39.7 ± 0.8mV vs-48.1 ± 1.6 mV,P < 0.001),and maximal outward current was similar (27.1 ± 1.5 pA/pF vs 25.7 ± 2.0 pA/pF,P > 0.05);(b) The NO donor sodium nitroprusside (SNP) increased outward currents only in CM (25.9 ± 1.9 to 46.7 ± 4.2 pA/pF,P < 0.001) but not SM (23.2 ± 3.1 to 27.0 ± 3.4 pA/pF,P > 0.05);(c) SNP added in the presence of the BK Ca antagonist iberiotoxin (IbTX) produced no increase in the outward current in CM (17.0 ± 2.8 vs 13.7 ± 2.2,P > 0.05);and (d) L-NNA caused a small insignificant inhibition of outward K + currents in both muscles;and (2) Muscle strip studies:(a) Blockade of the nerves with tetrodotoxin (TTX),or BK Ca with IbTX had no significant effect on resting tone of either muscle;and (b) SNP reduced tone in both muscles,and was unaffected by the presence of TTX or IbTX.CONCLUSION:Exogenous NO activates BK Ca only in CM of the cat.However,as opposed to other species,exogenous NO-induced relaxation is predominantly by a non-BK Ca mechanism,and endogenous NO has minimal effect on resting tone. 关键词：Circular smooth muscle FELINE K+ channel Lower esophageal SPHINCTER NITRIC oxide SLING TONE

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Nitric oxide activation of a potassium channel (BK_(Ca)) in feline lower esophageal sphincter

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