Jd. Escolar et al., ARCHITECTURE, ELASTIC FIBER, AND COLLAGEN IN THE DISTAL AIR PORTION OF THE LUNG OF THE 18-MONTH-OLD RAT, The Anatomical record, 248(1), 1997, pp. 63-69
Background: The increase in the distal air spaces which takes place wi
th age is the only sufficiently documented datum for differentiation b
etween the senile and the adult lung. There are other pulmonary compon
ents which may be modified as the lung enters the phase of old age, bu
t they have not as yet been sufficiently studied, The purpose of this
study is to make a morphometric comparison between the wall thickness
of the distal air spaces, elastic fiber, and collagen in lungs of rats
of between 5 and 18 months of age. Methods: The left lung of each rat
was histologically processed for light microscopy, The sections were
contrasted using methylene blue, resorcin-fuchsin and Sirius red, Syst
ematic randomized sampling was used for the selection of the histologi
cal fields studied, Morphometric variables were studied, and were syst
ematized into three groups, namely: variables related with the alveola
r architecture, variables which quantify elastic fiber, and those whic
h quantify collagen. Results: The old animals exhibited significant di
fferences (p < 0.05) in the following variables: 1, In relation with t
he alveolar architecture, mean linear intercept, alveolar chord and wa
ll thickness increased, whereas internal alveolar perimeter and tissue
density decreased, 2. The relation elastic fiber density/lung tissue
density increased, None of the variables which quantify collagen displ
ayed significant differences. Conclusion: Our data lead us to consider
that the lungs of the old animals displayed, not only an enlargement
of the distal air spaces, but also a thickening of the alveolar wall a
nd an increase in elastic fiber in relation to the rest of the lung ti
ssue. (C) 1997 Wiley-Liss, Inc.