Enhanced Ca2+ sensitization of the bronchial smooth muscle contraction in antigen-induced airway hyperresponsive rats.
To investigate the alteration in acetylcholine (ACh)-induced increase in Ca2+ sensitization of bronchial smooth muscle contraction concurrent with the airway hyperresponsiveness (AHR), the ACh-induced increases in cytosolic Ca2+ ([Ca2+]) level and contractile response were simultaneously determined by using Fura-2 loaded bronchial smooth muscle. The left main bronchi were isolated from AHR rats which were sensitized and repeatedly challenged with DNP-Ascaris antigen. The tissue ring preparations were incubated in loading solution containing 10 microM Fura-2AM for 3 hr at room temperature. Then the isometrical contraction and [Ca2+]i (F340/F380) were monitored. Although the ACh (10(-3) M)-induced contractile response in AHR group (322 +/- 60 % of 60 mM K+ induced contraction) was significantly greater than that in control animals (173 +/- 15 %, p<0.05), the ACh (10(-3) M)-induced increase in [Ca2+]i was without significant difference between the two groups (128 +/- 15 and 171 +/- 29% of 60 mM K+ -induced increase in [Ca2+]i, respectively). These findings suggest that an augmentation of ACh-induced Ca2+ sensitization may occur in bronchial smooth muscle of the rats with antigen-induced AHR.
Chiba
Y
Y
Department of Pharmacology, School of Pharmacy, Hoshi University, Tokyo, Japan. chiba@hoshi.ac.jp
Sakai
H
H
Suenaga
H
H
Kamata
K
K
Misawa
M
M
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D000941:Antigens / Q000494:pharmacology; D001980:Bronchi / Q000187:drug effects / Q000378:metabolism; D016535:Bronchial Hyperreactivity / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D000941:Antigens; D000109:Acetylcholine; D002118:Calcium