Basic Research
Copyright ©The Author(s) 2003. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Sep 15, 2003; 9(9): 2054-2059
Published online Sep 15, 2003. doi: 10.3748/wjg.v9.i9.2054
Role of calcium-activated potassium currents in CNP-induced relaxation of gastric antral circular smooth muscle in guinea pigs
Hui-Shu Guo, Zheng-Xu Cai, Hai-Feng Zheng, Xiang-Lan Li, Yi-Feng Cui, Zuo-Yu Wang, Wen-Xie Xu, Sang-Jin Lee, Young-Chul Kim
Hui-Shu Guo, Hai-Feng Zheng, Xiang-Lan Li, Yi-Feng Cui, Zuo-Yu Wang, Wen-Xie Xu, Department of Physiology, College of Medicine, Yanbian University, Yanji 133000, Jilin Province, China
Wen-Xie Xu, Center of Experiment, Affiliated Hospital of College of Medicine, Yanbian University, Yanji 133000, Jilin Province, China
Zheng-Xu Cai, the First Clinical Hospital of Jilin University, Changchun 130000, Jilin Province, China
Sang-Jin Lee, Young-Chul Kim, Department of Physiology, College of Medicine, Chungbuk National University, Cheongju, Chungbuk, 361-763, Korea
Author contributions: All authors contributed equally to the work.
Supported by the National Natural Science Foundation of China, No. 30160028
Correspondence to: Dr. Wen-Xie Xu, Department of Physiology, College of Medicine, Yanbian University, Juzi 121 Street, Yanji 133000, Jilin Province, China. wenxiexu@ybu.edu.cn
Telephone: +86-433-2660586 Fax: +86-433-2659795
Received: May 13, 2003
Revised: May 23, 2003
Accepted: June 27, 2003
Published online: September 15, 2003
Abstract

AIM: To investigate ion channel mechanism in CNP-induced relaxation of gastric circular smooth muscle in guinea pigs.

METHODS: Spontaneous contraction of gastric smooth muscle was recorded by a four-channel physiograph. The whole cell patch-clamp technique was used to record calcium-activated potassium currents and membrane potential in the gastric myocytes isolated by collagenase.

RESULTS: C-type natriuretic peptide (CNP) markedly inhibited the spontaneous contraction in a dose-dependent manner in gastric circular smooth muscle in guinea pigs. Ly83583, an inhibitor of guanylate cyclase, weakened CNP-induced inhibition on spontaneous contraction but Zaparinast, an inhibitor of cGMP sensitive phosphoesterase, potentiated CNP-induced inhibition in gastric circular smooth muscles. The inhibitory effects of CNP on spontaneous contraction were blocked by tetrathylammonium (TEA), a nonselective potassium channel blocker. C N P hyperpolarized membrane potential from -60.0 mV ± 2.0 mV to -68.3 mV ± 3.0 mV in a single gastric myocyte. CNP increased calcium-activated potassium currents (IK(ca)) in a dose-dependent manner in gastric circular myocytes. CNP also increased the spontaneously transient outward currents (STOCs). Ly83583 partly blocked CNP-induced increase of calcium-activated potassium currents, but Zaparinast potented the effect.

CONCLUSION: CNP inhibits spontaneous contraction, and potassium channel may be involved in the process in gastric circular smooth muscle of guinea pigs. CNP-induced increase of IK(ca) is mediated by a cGMP dependent pathway.

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