Selected contribution: effect of chronic passive length change on airway smooth muscle length-tension relationship.
The ability of rabbit trachealis to undergo plastic adaptation to chronic shortening or lengthening was assessed by setting the muscle preparations at three lengths for 24 h in relaxed state: a reference length in which applied force was approximately 1-2% of maximal active force (P(o)) and lengths considerably shorter and longer than the reference. Passive and active length-tension (L-T) curves for the preparations were then obtained by electrical field stimulation at progressively increasing muscle length. Classically shaped L-T curves were obtained with a distinct optimal length (L(o)) at which P(o) developed; however, both the active and passive L-T curves were shifted, whereas P(o) remained unchanged. L(o) was 72% and 148% that of the reference preparations for the passively shortened and lengthened muscles, respectively. The results suggest that chronic narrowing of the airways could induce a shift in the L-T relationship of smooth muscle, resulting in a maintained potential for maximal force production.
Wang
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Pulmonary Research Laboratory, St. Paul's Hospital, Vancouver, BC, Canada V6Z 1Y6.
Paré
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Seow
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D000222:Adaptation, Physiological; D000818:Animals; D001249:Asthma / Q000503:physiopathology; D046508:Culture Techniques; D004558:Electric Stimulation; D008168:Lung / Q000502:physiology*; D008173:Lung Diseases, Obstructive / Q000503:physiopathology; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000502:physiology*; D011817:Rabbits; D013997:Time Factors; D014132:Trachea / Q000502:physiology