Effects of Y-27632 on acetylcholine-induced contraction of intact and permeabilized intrapulmonary bronchial smooth muscles in rats.
In the present study, the effects of a selective Rho-associated coiled-coil forming protein kinase (ROCK) inhibitor, Y-27632 [(+)-(R)-trans-4-(1-aminoethyl)-(4-pyridyl)cyclohexanecarboxamide dihydrochloride] on acetylcholine-induced contraction and Ca(2+) sensitization of rat bronchial smooth muscle were examined. Intact and beta-escin-permeabilized muscles of the third branch of intrapulmonary bronchi were used. In intact muscles, Y-27632 (10(-6)-10(-4) M) concentration-dependently inhibited acetylcholine-induced contractile responses. In acetylcholine (10(-3) M)-precontracted intact muscles, the maximal relaxation (about 50% inhibition of contraction) was obtained by a concentration of 10(-4) M Y-27632, which had no effect on the resting tone. In beta-escin-permeabilized muscles, addition of acetylcholine (10(-5)-10(-3) M) plus GTP (100 microM) induced a further contraction, i.e., Ca(2+) sensitization at a constant Ca(2+) concentration of pCa=6.0. The acetylcholine-induced Ca(2+) sensitization was completely blocked in the presence of 10(-4) M Y-27632, whereas the Ca(2+)-induced contraction itself was not affected by Y-27632. Immunoblot study revealed the expression of ROCK-I and ROCK-II proteins in the intrapulmonary bronchi of rats. These findings suggest that Y-27632 dilates acetylcholine-mediated contraction of rat bronchial smooth muscle by inhibiting RhoA/ROCK-mediated Ca(2+) sensitization.
Chiba
Y
Y
Department of Pharmacology, School of Pharmacy, Hoshi University, 2-4-41 Ebara, Shinagawa, Tokyo 142-8501, Japan. chiba@hoshi.ac.jp
Takeyama
H
H
Sakai
H
H
Misawa
M
M
D000109:Acetylcholine / Q000494:pharmacology*; D000577:Amides / Q000494:pharmacology*; D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D002118:Calcium / Q000494:pharmacology; D002463:Cell Membrane Permeability; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D015151:Immunoblotting; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013047:Specific Pathogen-Free Organisms; D054460:rho-Associated Kinases
D000577:Amides; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; C108830:Y 27632; D006160:Guanosine Triphosphate; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D000109:Acetylcholine; D002118:Calcium