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Am J Physiol Lung Cell Mol Physiol 291: L281-L288, 2006. First published April 28, 2006; doi:10.1152/ajplung.00320.2005
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A novel bronchial ring bioassay for the evaluation of small airway smooth muscle function in mice

John Q. Liu, Dennis Yang, and Rodney J. Folz

Division of Pulmonary, Allergy, and Critical Care Medicine, Departments of Medicine and Cell Biology, Duke University Medical Center, Durham, North Carolina

Submitted 20 July 2005 ; accepted in final form 1 March 2006

Advances in our understanding of murine airway physiology have been hindered by the lack of suitable, ex vivo, small airway bioassay systems. In this study, we introduce a novel small murine airway bioassay system that permits the physiological and pharmacological study of intrapulmonary bronchial smooth muscle via a bronchial ring (BR) preparation utilizing BR segments as small as 200 µm in diameter. Using this ex vivo BR bioassay, we characterized small airway smooth muscle contraction and relaxation in the presence and absence of bronchial epithelium. In control BRs, the application of mechanical stretch is followed by spontaneous bronchial smooth muscle relaxation. BRs pretreated with methacholine (MCh) partially attenuate this stretch-induced relaxation by as much as 42% compared with control. MCh elicited a dose-dependent bronchial constriction with a maximal tension (Emax) of 8.7 ± 0.2 mN at an EC50 of 0.33 ± 0.02 µM. In the presence of nifedipine, ryanodine, 2-aminoethoxydiphenyl borate, and SKF-96365, Emax to MCh was significantly reduced. In epithelium-denuded BRs, MCh-induced contraction was significantly enhanced to 11.4 ± 1.0 mN with an EC50 of 0.16 ± 0.04 µM (P < 0.01). Substance P relaxed MCh-precontracted BR by 62.1%; however, this bronchial relaxation effect was completely lost in epithelium-denuded BRs. Papaverine virtually abolished MCh-induced constriction in both epithelium-intact and epithelium-denuded bronchial smooth muscle. In conclusion, this study introduces a novel murine small airway BR bioassay that allows for the physiological study of smooth muscle airway contractile responses that may aid in our understanding of the pathophysiology of asthma.

bronchial ring; airway smooth muscle


Address for reprint requests and other correspondence: R. J. Folz, Duke Univ. Medical Center, Box 2620, Durham, NC 27710






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