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KCI등재 학술저널

MLCK and PKC Involvements via Gi and Rho A Protein in Contraction by the Electrical Field Stimulation in Feline Esophageal Smooth Muscle

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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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 N<sup>G</sup>-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 Ca<sup>2+</sup>-free buffer but reappeared in normal Ca<sup>2+</sup>- containing buffer indicating that the contraction was Ca<sup>2+</sup> dependent. 4-aminopyridine (4-AP), voltage-dependent K<sup>+</sup> channel blocker, significantly enhanced on-contraction. Aluminum fluoride (a G-protein activator) increased on-contraction. Pertussis toxin (a G<sub>i</sub> inactivator) and C3 exoenzyme (a rhoA inactivator) significantly decreased on-contraction suggesting that Gi or rhoA protein may be related with Ca<sup>2+</sup> and K<sup>+</sup> 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 Ca<sup>2+</sup>, 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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