High concentrations of landiolol, a beta(1)-adrenoceptor antagonist, stimulate smooth muscle contraction of the rat trachea through the Rho-kinase pathway.
OBJECTIVE
Gradually progressing contraction of airway smooth muscle is suggested to be due to the Rho-kinase signaling pathway. In our preliminary study in rat tracheas, landiolol, a beta(1)-adrenoceptor antagonist, at high doses caused gradually progressing contraction, and this contraction reached a plateau after 20 min. Therefore, this study was carried out to clarify whether landiolol could stimulate the Rho-kinase pathway or the phosphatidylinositol (PI) response in the rat trachea.


METHODS
Seventy-eight male Wistar rats weighing 250-350 g were used for the experiments. Their tracheas were cut into 3-mm-wide ring segments or 1-mm-wide slices. Measurements of isometric tension and [(3)H] inositol monophosphate (IP(1)) production were conducted, using these tracheal rings or slices. Data values are expressed as means +/- SD, and statistical significance (P < 0.05) was determined using analysis of variance (ANOVA).


RESULTS
Landiolol (700 microM)-induced contraction was completely inhibited by fasudil at 30 microM, while the landiolol-induced contraction was not inhibited by 4-diphenylacetoxy-N-methyl-piperidine methobromide (4-DAMP), ketanserin, or nicardipine. Landiolol did not stimulate IP(1) production.


CONCLUSIONS
These results suggest that high concentrations of landiolol could cause airway smooth muscle contraction through the Rho-kinase pathway, but not through the PI response coupled with muscarinic M(3) receptors, 5-HT receptors or the activation of L-type Ca(2+) channels.
Shibata
Osamu
O
Department of Anesthesiology, Nagasaki University School of Medicine, Nagasaki, Japan.
Nishioka
Kenji
K
Yamaguchi
Masakazu
M
Makita
Tetsuji
T
Sumikawa
Koji
K
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D014132:Trachea / Q000187:drug effects* / Q000502:physiology; D016896:Treatment Outcome; D014508:Urea / Q000031:analogs & derivatives* / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000502:physiology*
D000319:Adrenergic beta-Antagonists; D009025:Morpholines; C077049:landiolol; D014508:Urea; D054460:rho-Associated Kinases