Journal of Applied Physiology, Vol 67, Issue 2 713-719, Copyright © 1989 by American Physiological Society
Epithelial modulation of trachealis muscle tension is calcium and temperature dependent
A. Lev, G. C. Christensen, J. P. Ryan, M. Wang and S. G. Kelsen
Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
The tracheobronchial epithelium produces inhibitory substance(s) that alter
the tracheal smooth muscle tension. This study examined the effect of
changes in extracellular Ca2+ and temperature in vitro on the tension
response of rabbit trachealis muscle to mechanical removal of the
epithelium. Tension during acetylcholine- and KCl-induced contractions was
examined at 0, 0.75, 1.5, 2.5, and 5 mM bath Ca2+ concentrations and at 37,
30, 23, and 41 degrees C bath temperature. At most extracellular Ca2+
concentrations (i.e., 0.75, 1.5, 2.5, and 5 mM), epithelial removal shifted
the acetylcholine concentration response approximately one-half log to the
left (P less than 0.001 for each condition) but had no effect on the
responses to KCl (P = NS). Reductions in bath Ca2+ to 0 mM eliminated the
epithelial inhibitory effect on the acetylcholine response. In contrast to
the effects of reductions in Ca2+, cooling the airway to 30 and 23 degrees
C progressively diminished the magnitude of the epithelial inhibitory
effect. Our results indicate that the influence of the tracheal epithelium
on tracheal smooth muscle responses to constrictor agonists is substance
specific and can be diminished by reductions in tracheal temperature and
extracellular Ca2+ concentration.
