Regulation of capacitative and noncapacitative receptor-operated Ca2+ entry by rho-kinase in tracheal smooth muscle.
To determine the mechanisms of Ca2+ mobilization induced by receptor agonists, we examined the role of Rho-kinase on the sarcoplasmic reticulum (SR) Ca2+ stores-dependent and -independent Ca2+ influx in guinea pig tracheal smooth muscle (TSM). Isometric tension and intracellular Ca2+ concentration ([Ca2+]i) were simultaneously measured using fura-2-loaded tissues. Depletion of the SR Ca2+ stores by thapsigargin caused an increase in [Ca2+]i and contraction, demonstrating capacitative Ca2+ entry (CCE). Because CCE was not inhibited by nifedipine, voltage-operated Ca2+ channels are not involved in CCE. Under the condition that CCE is fully activated, methacholine (MCh) and histamine caused further increases in [Ca2+]i and tension, demonstrating noncapacitative receptor-operated Ca2+ entry (non-CCE). The Ca2+ influx and contraction via non-CCE was inhibited by Y-27632, a Rho-kinase inhibitor, in a concentration-dependent fashion. In contrast, Y-27632 did not affect thapsigargin-induced CCE. Cytochalasin D, which disrupts actin cytoskeleton, inhibited contraction induced by CCE or MCh with no change in [Ca2+]i. Our results indicate that not only CCE but also non-CCE exist in TSM and that the latter is regulated by Rho-kinase, independent of actin cytoskeleton. In conclusion, Ca2+ influx regulated by the RhoA/Rho-kinase pathway may play a functional role in contraction by agonists.
Ito
Satoru
S
Second Department of Internal Medicine, School of Medicine, Nagoya University, Nagoya, Japan.
Kume
Hiroaki
H
Yamaki
Kenichi
K
Katoh
Hideki
H
Honjo
Haruo
H
Kodama
Itsuo
I
Hayashi
Hideharu
H
D000199:Actins / Q000187:drug effects / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D006632:Histamine / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D016210:Methacholine Chloride / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015398:Signal Transduction; D014132:Trachea / Q000378:metabolism*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D000199:Actins; D000577:Amides; D002121:Calcium Channel Blockers; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; D016210:Methacholine Chloride; C108830:Y 27632; D006632:Histamine; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein