Disturbance of alveolar lining layer: effects on alveolar microstructure.
To further study the influence of altered surface tensions on alveolar micromechanics, we analyzed the structure-function relationships in excised rabbit lungs filled with or rinsed by a fluorocarbon (approximately 15 mN/m) or by hexadecane (approximately 25 mN/m). The lungs were fixed and dehydrated by vascular perfusion, and the tissue samples were analyzed by light, transmission, and scanning electron microscopy. We made three observations. 1) Pressure-volume (P-V) loops hexadecane-filled lungs are shifted to the left and coincide with those of saline-filled lungs, indicating near-zero interfacial tension. In accordance, the alveolar microstructure and surface area of hexadecane-filled lungs resemble those of saline-filled lungs. 2) The P-V loops of fluorocarbon-filled lungs are not shifted to the left but coincide with those of fluorocarbon-rinsed lungs. Under both conditions, the alveolar microstructure is qualitatively identical and the alveolar surface areas are markedly reduced compared with normal air-filled lungs. These findings show that fluorocarbon-filled or fluorocarbon-rinsed lungs are subjected to similar interfacial tensions at the alveolar level. 3) Hexadecane-rinsed lungs show a pear-shaped P-V curve and a complex surface texture of peripheral air spaces. These results, together with in vitro observations, suggest a metamorphic interplay between lung surfactant and hexadecane in lining the surface and determining the surface tension. Evidently, the effects of foreign liquids introduced into the lung on the structure-function relationship cannot accurately be predicted from their in vitro surface tensions. This fact should be considered in the development of artificial surfactants.
Bachofen
H
H
Department of Anatomy, University of Berne, Switzerland.
Schürch
S
S
Possmayer
F
F
D000399:Air Pressure; D000818:Animals; D015824:Blood-Air Barrier / Q000502:physiology*; D006651:Histocytochemistry; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D011650:Pulmonary Alveoli / Q000502:physiology* / Q000648:ultrastructure*; D011663:Pulmonary Surfactants / Q000378:metabolism; D011817:Rabbits; D013499:Surface Properties; D013500:Surface Tension; D016707:Tissue Fixation
D011663:Pulmonary Surfactants