ML-9, a myosin light chain kinase inhibitor, reduces intracellular Ca2+ concentration in guinea pig trachealis.
We investigated the effects of ML-9 [1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine], a myosin light chain kinase (MLCK) inhibitor, on intracellular Ca2+ concentration ([Ca2+]i), contraction induced by high K+ and an agonist, and capacitative Ca2+ entry in fura-2-loaded guinea pig tracheal smooth muscle. ML-9 inhibited both the increase in [Ca2+]i and the contraction induced by 60 mM K+, 1 microM methacholine or 1 microM thapsigargin, an inhibitor of the sarcoplasmic reticulum Ca2+-ATPase. However, another MLCK inhibitor, wortmannin (3 microM), inhibited the contraction elicited by these stimuli without affecting [Ca2+]i. Under the condition that the thapsigargin-induced contraction was fully suppressed by 3 microM wortmannin, 30 microM ML-9 caused a further decrease in [Ca2+]i. The inhibitory effects of ML-9 on [Ca2+]i and the contraction elicited by methacholine were similar to those of SKF-96365 (1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole hydrochloride), a Ca2+ channel blocker. These results indicate that ML-9 acts as a potent inhibitor of Ca2+-permeable channels independently of MLCK inhibition in tracheal smooth muscle.
Division of Respiratory Medicine, Department of Medicine, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa, Nagoya 466-8550, Japan.
Satoru
S
Ito
Hiroaki
H
Kume
Haruo
H
Honjo
Itsuo
I
Kodama
Hideki
H
Katoh
Hideharu
H
Hayashi
Kaoru
K
Shimokata
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D016257:Fura-2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D006168:Guinea Pigs; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D018721:Muscarinic Agonists / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D011188:Potassium / Q000502:physiology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism; D000077191:Wortmannin
D000730:Androstadienes; D001381:Azepines; D002121:Calcium Channel Blockers; D007093:Imidazoles; D018721:Muscarinic Agonists; D026902:Potassium Channel Blockers; D016210:Methacholine Chloride; C049925:fura-2-am; C056218:ML 9; D019284:Thapsigargin; D009219:Myosin-Light-Chain Kinase; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D011188:Potassium; D002118:Calcium; D016257:Fura-2; D000077191:Wortmannin