Journal of Applied Physiology, Vol 67, Issue 1 174-180, Copyright © 1989 by American Physiological Society

ARTICLES

Expression of airway contractile properties and acetylcholinesterase activity in swine

T. M. Murphy, R. W. Mitchell, J. S. Blake, M. M. Mack, E. A. Kelly, N. M. Munoz and A. R. Leff
Department of Pediatrics, LaRabida Children's Hospital, Chicago, Illinois.

We studied the effect of maturation on contractile properties of tracheal smooth muscle from seventeen 2-wk-old swine (2ws) and fifteen 10-wk-old swine (10ws) in situ and in vitro. The response to parasympathetic stimulation was studied in situ in isometrically fixed segments. Contraction was elicited at lower frequencies [half-maximal response to electrical stimulation (ES50) = 6.7 +/- 0.05 Hz] in 2ws than in 10ws (ES50 = 9.1 +/- 0.4 Hz; P less than 0.01). Despite substantial differences in morphometrically normalized cross-sectional area in 2ws (0.012 +/- 0.003 cm2) and 10ws (0.028 +/- 0.001 cm2; P less than 0.01), maximal active tension elicited by parasympathetic stimulation was similar (12.4 +/- 3.2 g/cm in 2ws vs. 13.3 +/- 2.3 g/cm in 10ws; P = NS). In separate in vitro studies in 25 tracheal smooth muscle strips from 10 swine, concentration-response curves generated with potassium-substituted Krebs solution (KCl) were similar in 2ws and 10ws. In 58 other strips (10 swine), maximal active force elicited with acetylcholine (ACh) in 2ws was significantly greater than for 10ws (P less than 0.001). Removal of the epithelium had no effect. However, cholinesterase inhibition with 10(-7) M physostigmine augmented the response to ACh in 10ws (P less than 0.02) but not 2ws. We demonstrate increased force generation and sensitivity to vagal stimulation in 2ws vs. 10ws, which corresponds to increased reactivity to ACh in vitro. The relative hyperresponsiveness in 2ws is specific for cholinergic response and is attenuated at least in part by maturation of the activity of acetylcholinesterase enzyme.

This article has been cited by other articles:

				R. Ramchandani, X. Shen, S. J. Gunst, and R. S. Tepper Comparison of elastic properties and contractile responses of isolated airway segments from mature and immature rabbits J Appl Physiol, July 1, 2003; 95(1): 265 - 271. [Abstract] [Full Text] [PDF]

				R. E. Malmstrom, D. C. Tornberg, G. Settergren, J. Liska, M. Angdin, J. O. Lundberg, and E. Weitzberg Endogenous Nitric Oxide Release by Vasoactive Drugs Monitored in Exhaled Air Am. J. Respir. Crit. Care Med., July 1, 2003; 168(1): 114 - 120. [Abstract] [Full Text] [PDF]

				P. Chitano, J. Wang, C. M. Cox, N. L. Stephens, and T. M. Murphy Different ontogeny of rate of force generation and shortening velocity in guinea pig trachealis J Appl Physiol, April 1, 2000; 88(4): 1338 - 1345. [Abstract] [Full Text] [PDF]

				M. E. Wylam, N. Gungor, R. W. Mitchell, and J. G. Umans Eosinophils, major basic protein, and polycationic peptides augment bovine airway myocyte Ca2+ mobilization Am J Physiol Lung Cell Mol Physiol, June 1, 1998; 274(6): L997 - L1005. [Abstract] [Full Text] [PDF]