Am. J. Respir. Crit. Care Med., Volume 158, Number 5, November 1998, 1607-1612

Human Lung Parenchyma Responds to Contractile Stimulation

M. DOLHNIKOFF, J. MORIN, and M. S. LUDWIG

Meakins-Christie Laboratories, Department of Medicine, Royal Victoria Hospital, and Department of Surgery, Royal Victoria Hospital, McGill University, Montreal, Canada

Tissue resistance increases after agonist challenge. Parenchymal contractile cells may be the responsible element. We investigated the viscoelastic properties of human parenchymal strips before and after challenge with acetylcholine (ACh) (10³ M). Thirteen subpleural strips were oscillated in the organ bath, and measurements of resistance (R), elastance (E), and hysteresivity () were obtained. After physiologic measurements, tissues were fixed for morphometric and immunohistochemical analysis. We quantitated the volume proportion of alveolar, airway, and blood vessel wall in individual strips. Smooth-muscle-specific actin was identified using a monoclonal antibody and the volume proportion of actin quantitated by point counting. After ACh, there was a significant increase in tension (2.6 ± 0.6%), R (11.0 ± 1.8%), E (4.3 ± 0.7%), and  (8.2 ± 2.4%) (p < 0.002). Four strips contained no identifiable airways, yet in strips with and without airways there was no difference in the magnitude of the mechanical response or in the volume proportion of smooth-muscle-specific actin in the alveolar walls. We conclude that human lung parenchymal strips respond to ACh challenge with changes in dynamic mechanical behavior. Furthermore, small airways are not required for such a response to occur. This implicates a direct contractile response at the level of the alveolar wall and/or the alveolar duct.

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