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KMID : 0811720100140010029
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Korean Journal of Physiology & Pharmacology
2010 Volume.14 No. 1 p.29 ~ p.35
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MLCK and PKC Involvements via Gi and Rho A Protein in Contraction by the Electrical Field Stimulation in Feline Esophageal Smooth Muscle
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Park Sun-Young
Shim Je-Ho
Kim Mi-Na
Sun Yih-Hsiu
Kwak Hyun-Soo
Yan Xiang-Mei
Choi Byung-Chul
Im Cha-Euk
Sim Sang-Soo
Jeong Ji-Hoon
Kim In-Kyeom
Sohn Uy-Dong
Min Young-Sil
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Abstract
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We have shown that myosin light chain kinase (MLCK) was required for the off-contraction in response to the electrical field stimulation (EFS) of feline esophageal smooth muscle. In this study, we investigated whether protein kinase C (PKC) may require the on-contraction in response to EFS using feline esophageal smooth muscle. The contractions were recorded using an isometric force transducer. On-contraction occurred in the presence of NG-nitro-L-arginine methyl ester (L-NAME), suggesting that nitric oxide acts as an inhibitory mediator in smooth muscle. The excitatory composition of both contractions was cholinergic dependent which was blocked by tetrodotoxin or atropine. The on-contraction was abolished in Ca2＋-free buffer but reappeared in normal Ca2＋- containing buffer indicating that the contraction was Ca2＋ dependent. 4-aminopyridine (4-AP), voltage-dependent K＋ channel blocker, significantly enhanced on-contraction. Aluminum fluoride (a G-protein activator) increased on-contraction. Pertussis toxin (a Gi inactivator) and C3 exoenzyme (a rhoA inactivator) significantly decreased on-contraction suggesting that Gi or rhoA protein may be related with Ca2＋ and K＋ channel. ML-9, a MLCK inhibitor, significantly inhibited on-contraction, and chelerythrine (PKC inhibitor) affected on the contraction. These results suggest that endogenous cholinergic contractions activated directly by low-frequency EFS may be mediated by Ca2＋, and G proteins, such as Gi and rhoA, which resulted in the activation of MLCK, and PKC to produce the contraction in feline distal esophageal smooth muscle.
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KEYWORD
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Electrical field stimulation, Smooth muscle, Ca2＋, K＋, G protein, On contraction, Esophagus
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