MLCK and PKC Involvements via Gi and Rho A Protein in Contraction by the Electrical Field Stimulation in Feline Esophageal Smooth Muscle.
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.
Park
Sun Young
SY
College of Pharmacy, Chung-Ang University, Seoul 156-756, Korea.
Shim
Jae Ho
JH
Kim
Mina
M
Sun
Yih Hsiu
YH
Kwak
Hyun Soo
HS
Yan
Xiangmei
X
Choi
Byung-Chul
BC
Im
Chaeuk
C
Sim
Sang Soo
SS
Jeong
Ji Hoon
JH
Kim
In Kyeom
IK
Min
Young Sil
YS
Sohn
Uy Dong
UD