APStracts 2:0141L, 1995.

Alveolar surfactant aggregate conversion in ventilated normal and injured rabbits. Veldhuizen, Ruud A. W., John Marcou, Li-Juan Yao, Lynda McCaig, Yushi Ito, and James F. Lewis. Departments of Physiology and Medicine, The University of Western Ontario, London, Ontario, Canada N6A 5A5.

APStracts 2:0141L, 1995.

Alveolar surfactant can be separated into two subtypes; large aggregates and small aggregates. Large aggregates represent the surface active form of surfactant and are the metabolic precursors of small aggregates. Previous studies examined the mechanism by which large aggregates are converted into small aggregates in vitro. We have used intratracheal injection of radiolabelled large aggregates in rabbits to probe the aggregate conversion in vivo. Following this injection, animals were mechanically ventilated for 60 minutes. After sacrifice, the lungs were lavaged and the percentage of radiolabel present in the small aggregate fraction was determined. Our results showed that ventilation resulted in aggregate conversion, and that increases in tidal volume, but not in respiratory rate, correlated with increased conversion. Aggregate conversion in rabbits with acute lung injury correlated significantly with severity of injury. We conclude that a change in surface area (ie respiration), is necessary for aggregate conversion in vivo and that the ventilation strategy can affect this conversion. Furthermore, increased aggregate conversion in injured lungs might contribute to increased small to large aggregate ratios in these lungs compared to normal lungs.

Received 9 May 1995; accepted in final form 9 August 1995.
APS Manuscript Number L141-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.