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 ∼1–2% of maximal active force (Po) 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 Podeveloped; however, both the active and passive L-T curves were shifted, whereas Po 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.