AJP - Lung Cellular and Molecular Physiology, Vol 266, Issue 6 713-L721, Copyright © 1994 by American Physiological Society
Confocal imaging of time-dependent internalization and localization of NBD-PC in intact rat lungs
M. R. Chinoy, A. B. Fisher and H. Shuman
Institute for Environmental Medicine, School of Medicine, University of Pennsylvania, Philadelphia 19104.
Morphological localization of a fluorescent analogue of phosphatidylcholine
(PC), C12-NBD-PC ([1-palmitoyl-2-[12-(7-nitro-2-1,3-benzoxadiazol-4-yl)
amino] dodecanoyl]PC) was evaluated in adult rat lung. Fluorescence was
observed at various times after intratracheal liposome instillation.
Fluorometric analysis of C12-NBD-PC in lung homogenate showed an initial
rapid uptake followed by a more gradual uptake phase. Microscopic
observation of fixed lung slices showed C12-NBD-PC uptake in alveolar type
II cells (identified by surfactant protein A and Maclura pomifera
agglutinin colocalization), nonciliated distal airway epithelial cells, but
not in subepithelial tissue. Macrophages showed an initial uptake that did
not increase with time. Fluorescence measured in type II cells was diffuse
at 5 min, became punctate, and intensified gradually by 2 h. Isolation of
type II cells and lamellar bodies from instilled lung confirmed
localization of fluorophore in them. This study shows time-dependent uptake
of C12-NBD-PC by type II and bronchiolar cells and preferential
internalization to lung lamellar bodies as previously described for
surfactant PC.
