R. Breuer et al., RELATIONSHIP OF SECRETORY GRANULE CONTENT AND PROLIFERATIVE INTENSITYIN THE SECRETORY COMPARTMENT OF THE HAMSTER BRONCHIAL EPITHELIUM, American journal of respiratory cell and molecular biology, 8(5), 1993, pp. 480-485
We have previously shown that normal hamster airway epithelial secreto
ry cells have a lower proliferative intensity than basal cells, but be
cause of their high frequency are a major contributor to cell renewal
(Am. J. Respir. Cell Mol. Biol. 1990; 2:51-58). In the present experim
ent, the relation between proliferative intensity and secretory granul
e content in bronchial epithelial cells is studied. [H-3]thymidine (2
muCi/g wt) was given intraperitoneally, 1 h before killing, to 5 hamst
ers treated 21 days earlier with intratracheal saline and to six hamst
ers in which secretory cell metaplasia had been induced by intratrache
al treatment with 300 mug of human neutrophil elastase given 21 days e
arlier. Light microscopic autoradiograms were prepared from 2-mum-thic
k Epon sections of left intrapulmonary hilar bronchi. Cells were categ
orized as basal, ciliated, secretory, or indeterminate. Secretory cell
s were classified as either: S1, with 0 to 4 granules; S2, with greate
r-than-or-equal-to 5 granules with intervening cytoplasm; or S3, with
abundant granules and no apparent supranuclear cytoplasm. Proliferativ
e intensity was defined by the categorical labeling index (LI(c)) at 1
h after [H-3]thymidine injection. LI(c) was determined by the number
of labeled cells in a category as die percent of labeled and unlabeled
cells of that category. LI(c) of each of the cell categories were sim
ilar in the elastase and saline groups. LI(c) was highest for basal ce
lls, reflecting their proliferative intensity, and lowest for ciliated
cells. In the saline group, LI(c) of S1 (0. 25 %) was significantly h
igher compared with S2 (0.13%); S3 cells were rare (0.2%) and none wer
e labeled. In the elastase group, S3 cell frequency was 22% and their
LI(c) (0.05%) was less than the LI(c) of S1 (0.21%) and S2 cells (0.59
%). We conclude that the proliferative intensity of bronchial secretor
y cells is heterogeneous and that granule-rich secretory cells have an
extremely low proliferative intensity. As with ciliated cells, this m
ay be associated with a higher state of differentiation.