Postnatal treatment with retinoic acid increases the number of
pulmonary alveoli in rats.
Massaro, Gloria D., Donald Massaro.
Lung Biology Laboratory and the Departments of Pediatrics and
Medicine, Georgetown University School of Medicine, Washington, D.C.
20007
APStracts 2:0223L, 1995.
Dexamethasone, a glucocorticosteroid hormone, inhibits the formation
of alveoli; retinoids and glucocorticosteroid hormones can be
mutually antagonistic. These observations led us to test the
hypothesis that the administration of retinoic acid to postnatal rats
would prevent the low alveolar number and the low body mass-specific
gas-exchange surface area (Sa) produced by treatment with
dexamethasone. We used serial lung sections to distinguish alveoli
from alveolar ducts and stereological procedures that allow
quantitation of alveoli uninfluenced by their size, shape, or
distribution. Treatment with retinoic acid prevented the low number
of alveoli and the low body mass-specific Sa caused by treatment with
dexamethasone. In otherwise untreated rats, retinoic acid caused a
50% increase in the number of alveoli but without an increase in Sa
suggesting the action of a regulatory mechanism to prevent unneeded
Sa. These findings provide the first experimental support for the
possibility that in individuals with too few alveoli for adequate gas
exchange, treatment with a pharmacological agent may provide
preventative or remedial therapy.
Received 30 August 1995; accepted in final form 4 December 1995.
APS Manuscript Number L263-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 12 December 95