Effects of myosin light chain kinase inhibitors on carbachol-activated nonselective cationic current in guinea-pig gastric myocytes.
The effects of myosin light chain kinase inhibitors on muscarinic stimulation-activated nonselective cationic current (ICCh) in guinea-pig gastric antral myocytes were studied using the whole-cell patch-clamp technique. ICCh was induced by carbachol (CCh, 50 microM) at a holding potential of -30 mV or -60 mV. ML-7, a chemical inhibitor of myosin light chain kinase (MLCK), inhibited ICCh concentration dependently in a reversible manner (53 +/- 8.6% at 1 microM, mean +/- SE, n = 11). In addition, amplitudes of ICCh were only 37 +/- 2.7% of the daily control values following the addition of a peptide inhibitor of MLCK to the pipette solution. On the other hand, ML-7 had an inhibitory effect on voltage-operated Ca2+ channel current. The peak value of Ba2+ current at 0 mV was reduced to 35 +/- 7.4% (n = 9) by 3 microM of ML-7. As ICCh is known to have an intracellular Ca2+ dependence, we tried to exclude the possibility that ML-7 inhibited ICCh indirectly via suppression of Ca2+ current and the similar inhibitory effects of ML-7 on ICCh were confirmed under the following conditions: (1) clamp of membrane potential at -60 mV; (2) clamp of intracellular [Ca2+] to 1 microM by 10 mM BAPTA; (3) pre-inhibition of Ca2+ channel by verapamil. Different from the effects on ICCh, ML-7 barely inhibited the same cationic current induced by guanosine 5'-O-(3-thiotriphosphate) (GTP[gammaS], 0.2 mM) in the pipette solution. These results suggest that a Ca2+/calmodulin-MLCK-dependent pathway can modulate the activation of ICCh in guinea-pig gastric antral myocytes.
Kim
Y C
YC
Department of Physiology and Biophysics, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Korea.
Kim
S J
SJ
Kang
T M
TM
Suh
S H
SH
So
I
I
Kim
K W
KW
D000818:Animals; D001381:Azepines / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology*; D002412:Cations / Q000378:metabolism*; D004553:Electric Conductivity; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D009281:Naphthalenes / Q000494:pharmacology*; D013270:Stomach / Q000166:cytology / Q000502:physiology*
D001381:Azepines; D002412:Cations; D004791:Enzyme Inhibitors; D009281:Naphthalenes; C070571:ML 7; D002217:Carbachol; D009219:Myosin-Light-Chain Kinase