Effects of smooth muscle activation on axial mechanical properties of excised canine
bronchi.
Shardonofsky, Felix R., Todd M. Officer, Aladin M. Boriek, and Joseph R. Rodarte.
Departments of Pediatrics1 and Medicine,2 Baylor College of Medicine, Houston,
Texas 77030
APStracts 8:0007A, 2001.
This study tested the hypothesis that airway smooth muscle (ASM) activation produces
an airway active axial force (AAAF). Bronchi (n = 10) immersed in a tissue bath
containing 95% O2-5% CO2-equilibrated Krebs solution were subjected to passive axial
lengthening and shortening at 0-20 cmH2O of transmural pressure. ASM was relaxed
with isoproterenol and activated with methacholine. Axial tensile (epsilonx), transverse
compressive (epsilony), and shear strains (epsilonxy) were computed from the
displacements of four markers placed onto the specimen's surface. The AAAF was
estimated by subtracting the control axial force (AF) values at a given epsilonx from
those obtained after methacholine. epsilonx-AF relationships were curvilinear, with
maximum epsilonx being approached at ~15 g of AF. The epsilony decreased during
bronchial lengthening. Cholinergic stimulation produced 1) a decrease of both epsilonx
and epsilony at a given AF relative to control, indicating ASM shortening, and 2) an
AAAF that increased with increasing epsilonx and transmural pressure. A portion of the
work of expanding the lungs is required to lengthen the airways, and, therefore, an AAAF
would increase lung elastance and recoil.
Received 30 October 2000; accepted in final form 6 November 2000
APS Manuscript Number A0975-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 29 January 2001