Am. J. Respir. Cell Mol. Biol., Vol 10, No. 3, 03 1994, 259-270.
Regulation of Clara cell 10 kD protein secretion by pilocarpine: quantitative comparison of nonciliated cells in rat bronchi and bronchioles based on laser scanning confocal microscopy
DE Dodge, CG Plopper and RB Rucker
Department of Pharmacology and Toxicology, School of Veterinary Medicine, University of California, Davis 95616.
Standard immunohistochemical techniques and laser scanning confocal
microscopy were used to assess changes in the abundance of Clara cell 10 kD
protein (CC10) within granules and endoplasmic reticulum of rat nonciliated
cells after the administration of the secretagogue pilocarpine.
Intracellular pools of CC10 were compared over time with time-matched
controls at two airway levels, proximal bronchi and terminal bronchioles.
Three zones of reflectance intensity (high, medium, and low), corresponding
to different densities of CC10 were used to quantify changes in CC10
levels. We observed a shift in the abundance of CC10 from endoplasmic
reticulum to granules 30 min after injection of pilocarpine. In addition,
the depletion of granule-based CC10 occurred earlier in bronchial cells (30
min) than in bronchiolar cells (60 min). We also noted that the density of
CC10 within the two cellular compartments remained steady even though the
levels of CC10 dropped due to degranulation. Following degranulation, CC10
levels returned to near-control levels. In the absence of pilocarpine, the
percentage of cell volume occupied by the granule-based CC10 indicated that
two varieties of nonciliated cells exist in bronchial airways. However,
administration of pilocarpine abolishes this difference in CC10 abundance.
Our results demonstrate that bronchial cells respond sooner to the
secretagogue than do their bronchiolar counterparts and/or possess
biosynthetic capabilities that are more easily overwhelmed than those of
the terminal bronchiolar cells. These differences suggest that proximal
nonciliated cells are distinct from distal nonciliated cells.
