Jpn. J. Pharmacol. 84 (2), 221-224 (2000)

Acetylcholine-Induced Smooth Muscle Contraction of Intrapulmonary Small Bronchi Is Augmented in Antigen-Induced Airway Hyperresponsive Rats

Yoshihiko Chiba*, Yuka Takada, Hiroyasu Sakai, Hisao Takeyama and Miwa Misawa

Department of Pharmacology, School of Pharmacy, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan
*Corresponding author.ĘFAX:+81-3-5498-5787

Abstract: Smooth muscle responsiveness of intrapulmonary small bronchi obtained from repeatedly antigen-challenged rats was compared with that from control animals to determine whether smooth muscle contractility of peripheral airways is augmented by such repeated challenge. In intact (non-permeabilized) smooth muscles of intrapulmonary bronchi, the acetylcholine (ACh)-induced contractile response was significantly augmented in the repeated challenge group, although 60-mM K+-induced contraction was within the normal level. In b-escin-permeabilized muscles, no significant difference between groups was observed in the Ca2+-induced contractile responses. Thus, augmented ACh-induced contraction of intact intrapulmonary small bronchial smooth muscle might be, at least in part, due to an enhanced ACh-mediated Ca2+-sensitizing signal.

Keywords: Airway hyperresponsiveness, Permeabilized intrapulmonary bronchial smooth muscle,
Ca2+ sensitization

CopyrightŠ The Japanese Pharmacological Society 2000

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