Journal of Applied Physiology, Vol 74, Issue 4 1613-1621, Copyright © 1993 by American Physiological Society

ARTICLES

Airway smooth muscle shortening in excised canine lung lobes

M. Okazawa, T. R. Bai, B. R. Wiggs and P. D. Pare
University of British Columbia, Pulmonary Research Laboratory, St. Paul's Hospital, Vancouver, Canada.

To estimate the importance of lung parenchymal airway interdependence in attenuating airway narrowing, airway smooth muscle shortening in response to nebulized carbachol was measured in excised canine lung lobes and compared with the calculated load applied by lung elastic recoil. Pulmonary resistance of matched right and left upper lobes of five dogs was measured in a pressure-compensated volume plethysmograph by forced oscillation (6 Hz) before and after administration of an aerosol of carbachol (250 mg/ml) or saline. Matched lobes were studied at transpulmonary pressures (PL) of 5, 7, 10, 12, and 15 cmH2O. The lungs were then fixed at that PL by pulmonary arterial perfusion with formaldehyde, and cross sections of multiple airways from each lobe (n = 275) were examined by use of morphometric techniques to measure luminal area and smooth muscle length. By use of the saline lobe as a control, percentage of muscle shortening and decrease in airway lumen area caused by carbachol could be calculated. Passive and active smooth muscle stresses in each airway were calculated from PL and the calculated change in peribronchial pressure for a given change in airway diameter. The increase in pulmonary resistance and average smooth muscle shortening after administration of carbachol was greater in lobes held at lower PL. There was marked variation in narrowing between airways within a lobe: smooth muscle shortening ranged between 0 and 65% but averaged < 45% at all levels of PL.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				C. Y. Seow Are you pulling my airway? Eur. Respir. J., November 1, 2005; 26(5): 759 - 761. [Full Text] [PDF]

				P. B. Noble, D. J. Turner, and H. W. Mitchell Relationship of airway narrowing, compliance, and cartilage in isolated bronchial segments J Appl Physiol, March 1, 2002; 92(3): 1119 - 1124. [Abstract] [Full Text] [PDF]

				L. Wang, R. Tepper, J. L. Bert, K. L. Pinder, P. D. Pare, and M. Okazawa Mechanical properties of the tracheal mucosal membrane in the rabbit. I. Steady-state stiffness as a function of age J Appl Physiol, March 1, 2000; 88(3): 1014 - 1021. [Abstract] [Full Text] [PDF]

				C. Y. Seow, L. Wang, and P. D. Pare Airway narrowing and internal structural constraints J Appl Physiol, February 1, 2000; 88(2): 527 - 533. [Abstract] [Full Text] [PDF]

				M. Okazawa, Y. D'Yachkova, and P. D. Pare Mechanical properties of lung parenchyma during bronchoconstriction J Appl Physiol, February 1, 1999; 86(2): 496 - 502. [Abstract] [Full Text] [PDF]

				V. Brusasco, E. Crimi, and R. Pellegrino Airway hyperresponsiveness in asthma: not just a matter of airway inflammation Thorax, November 1, 1998; 53(11): 992 - 998. [Full Text]

				P. T. MACKLEM The Mechanics of Breathing Am. J. Respir. Crit. Care Med., April 1, 1998; 157(4): S88 - S94. [Full Text] [PDF]