Mechanisms for the mechanical response of airway smooth muscle to length oscillation

• Published in: Journal of applied physiology (1985) Vol. 83; no. 3; pp. 731 - 738
• Main Authors: Shen, X, Wu, M. F, Tepper, R. S, Gunst, S. J
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.09.1997; American Physiological Society
• Subjects: Acetylcholine - pharmacology; Air breathing; Animals; Biological and medical sciences; Dogs; Fundamental and applied biological sciences. Psychology; In Vitro Techniques; Isometric Contraction - drug effects; Muscle Contraction - drug effects; Muscle Contraction - physiology; Muscle Relaxation - drug effects; Muscle, Smooth - drug effects; Muscle, Smooth - physiology; Respiratory Mechanics - drug effects; Respiratory Mechanics - physiology; Respiratory Physiological Phenomena; Respiratory System - drug effects; Respiratory system: anatomy, metabolism, gas exchange, ventilatory mechanics, respiratory hemodynamics; Trachea - drug effects; Trachea - physiology; Vertebrates: respiratory system; Fissipedia; Carnivora; Contractility; Tidal volume; Respiratory system; In vitro; Respiratory tract; Vertebrata; Mammalia; Reactivity; Ventilatory response; Oscillation; Mechanical stimulus; Dog; Trachea; Response stimulus relation
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1997.83.3.731

X. Shen, M. F. Wu, R. S. Tepper, and S. J. Gunst Departments of Physiology and Biophysics and of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202 Received 11 February 1997; accepted in final form 6 May 1997. Shen, X., M. F. Wu, R. S. Tepper, and S. J. Gunst. Mechanisms for the mechanical response of airway smooth muscle to length oscillation. J. Appl. Physiol. 83(3): 731-738, 1997. Airway smooth muscle tone in vitro is profoundly affected by oscillations in muscle length, suggesting that the effects of lung volume changes on airway tone result from direct effects of stretch on the airway smooth muscle. We analyzed the effect of length oscillation on active force and length-force hysteresis in canine tracheal smooth muscle at different oscillation rates and amplitudes during contraction with acetylcholine. During the shortening phase of the length oscillation cycle, the active force generated by the smooth muscle decreased markedly below the isometric force but returned to isometric force as the muscle was lengthened. Results indicate that at rates comparable to those during tidal breathing, active shortening and yielding of contractile elements contributes to the modulation of force during length oscillation; however, the depression of force during shortening cannot be accounted for by cross-bridge properties, shortening-induced cross-bridge deactivation, or active relaxation. We conclude that the depression of contractility may be a function of the plasticity of the cellular organization of contractile filaments, which enables contractile element length to be reset in relation to smooth muscle cell length as a result of smooth muscle stretch. tracheal smooth muscle; airway reactivity; contractile mechanisms; tidal breathing 0161-7567/97 $5.00 Copyright © 1997 the American Physiological Society