AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 5 783-R788, Copyright © 1986 by American Physiological Society
Development of bronchiolar epithelium in rats
G. D. Massaro and D. Massaro
We used ultrastructural and morphometric means to examine aspects of the
regulation of the maturation of rat bronchiolar Clara cells and the
development of the epithelium of small conducting airways in the perinatal
period. We found the nuclear numerical density per cubed centimeter (Nvn)
of Clara cells fell and the Nvn of ciliated cells increased from birth to
age 60 days, the prenatal administration of a glucocorticosteroid
(dexamethasone) to dams caused a 35% decrease in the Nvn of ciliated cells
present at birth but did not alter the Nvn of Clara cells, the
administration of dexamethasone to pups from postnatal days 1 to 6 did not
alter the Nvn of bronchiolar Clara or ciliated cells present at age 7 days
but did diminish the total number of lung cells as assessed by measurements
of lung DNA, the administration of dexamethasone to dams from gestation
days 18 to 20 or from gestation days 20 to 22 did not alter the volume
density of Clara cell glycogen, secretory granules, rough endoplasmic
reticulum, or mitochondria of pups at gestation day 21.5 or on the day of
birth, and glucagon, epinephrine, and 8-bromoadenosine 3',5'-cyclic
monophosphate resulted in a decrease of Clara cell glycogen when
individually incubated in vitro for 4 h with bronchiolar tissue from rat
fetuses 21.5 days of age.
