title: MLCK and PKC Involvements via Gi and Rho A Protein in Contraction by the Electrical Field Stimulation in Feline Esophageal Smooth Muscle.
abstract: 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(G)-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(2+)-free buffer but reappeared in normal Ca(2+)-containing buffer indicating that the contraction was Ca(2+) 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 G(i) inactivator) and C3 exoenzyme (a rhoA inactivator) significantly decreased on-contraction suggesting that Gi or rhoA protein may be related with Ca(2+) 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 Ca(2+), 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.
authors.affiliation: College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea.
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Park
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Shim
authors.forename: Mina
authors.initials: M
authors.lastname: Kim
authors.forename: Yih Hsiu
authors.initials: YH
authors.lastname: Sun
authors.forename: Hyun Soo
authors.initials: HS
authors.lastname: Kwak
authors.forename: Xiangmei
authors.initials: X
authors.lastname: Yan
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Choi
authors.forename: Chaeuk
authors.initials: C
authors.lastname: Im
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Sim
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Jeong
authors.forename: In Kyeom
authors.initials: IK
authors.lastname: Kim
authors.forename: Young Sil
authors.initials: YS
authors.lastname: Min
authors.forename: Uy Dong
authors.initials: UD
authors.lastname: Sohn