Publication: Stereologic analysis of the in vivo alveolar type II cell
response to isoproterenol or saline administration
Authors
Smith, Dennis M. ; Griffin, Lawrence S.
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Publisher
Murcia : F. Hernández
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DOI
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info:eu-repo/semantics/article
Description
Abstract
Previous studies have demonstrated enhanced
secretion of pulmonary surfactant from type I1 alveolar
epithelial cells following 8-adrenergic stimulation. The
present study was undertaken in order to provide
quantitative morphologic data supporting this effect in vivo.
Adult male Sprague-Dawley rats were injected
subcutaneously with 150 mg/kg L-isoproterenol, a widerange
8-adrenergic agonist, and killed at times 0.25 - 12
hours post-injection. Other rats were similarly injected with
saline, and killed at times 0.25 - 6 hours post-injection. A
third group of animals was not injected, nor handled, prior
to the time of death, and served as baseline controls.
Stereologic analysis of the intracellular organelles of the
type I1 celss in the animals treated with L-isoproterenol
revealed a significant decrease in lamellar body volume
density, indicating increased secretion of surfactant, at 0.5
- 4 hours. The rough endoplasmic reticulum volume density
increased significantly at 2 - 6 hours, indicating increased
synthetic activity. In contrast, the type I1 cells of salineinjected
animals showed no significant evidence of increased
secretion, but did demonstrate a large increase in synthetic
activity, resulting in many large lamellar bodies at 2 and
4 hours post-injection. The results of this study provide
quantitative morphological evidence of 8-adrenergic
stimulation of the secretion and synthesis of pulmonary
surfactant secretion by type I1 cells of the adult rat lung
in vivo. In addition, they suggest an enhancement of
surfactant synthesis following saline injection, which is
perhaps based on endogenous catecholamine release.
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