Am. J. Respir. Crit. Care Med., Vol 149, No. 3, Mar 1994, 759-766.
Development of gas-exchange surface area in rat lung. The effect of alveolar shape
LN Blanco and L Frank
Department of Medicine, University of Miami School of Medicine, FL 33101.
During development, the surface area of the gas-exchange region of the lung
can increase by: (1) expansion, (2) subdivision (septation), (3)
replication, or (4) change of shape of the basic gas-exchange units
(saccules or alveoli). We evaluated the shape of these units in rat lung
from birth to adulthood. A shape factor (phi g) was defined in terms of the
surface area (Sg) and the volume (Va) of the average unit, using the
expression phi g = SgVa-2/3. We studied the lungs of untreated animals and
of animals exposed to or treated with hyperoxia (> 95% O2) and/or
dexamethasone, each of which is known to inhibit septation in early
postnatal life, and with deferoxamine, which protects the lung against the
inhibitory effect of hyperoxia. The values found for the shape factor
showed no significant difference with regard to age or treatment. This
finding suggests that: (1) saccules and alveoli are formed with a certain
predetermined shape (close to a hemisphere), (2) any enlargement with time
is isotropic, (3) alveolar shape is insensitive to the drastic treatments
used, and (4) change of shape is not a mechanism used to increase the
gas-exchange surface area of the developing rat lung.
