Am. J. Respir. Cell Mol. Biol., Vol 10, No. 2, 02 1994, 177-183.
Effect of inhaled endotoxin on intraepithelial mucosubstances in F344 rat nasal and tracheobronchial airways
T Gordon and JR Harkema
Institute of Environmental Medicine, New York University Medical Center, Tuxedo 10987.
Increased sputum production and chronic bronchitis are associated with
occupational exposure to endotoxin-contaminated organic ducts. The present
study examined whether repeated exposure to occupationally relevant
concentrations of airborne endotoxin in the F344 rat can alter the volume
density of stored intraepithelial mucosubstances (Vs) in the respiratory
tract. Rats were exposed to saline or endotoxin aerosols for 3 h/day for 3
days and were killed 24 h after the last exposure. Quantitative
histochemistry of Vs in airway epithelium was examined at three distinct
levels of the respiratory tract (nose, trachea, and lung). Exposure to
endotoxin produced a dose-dependent increase in Vs in the intrapulmonary
airways. The quantity of Vs in the intrapulmonary airways was significantly
increased in animals exposed to as little as 0.3 micrograms/m3 endotoxin.
Significant increases in Vs were observed in the trachea only after
exposure to > or = 3.1 micrograms/m3 endotoxin, whereas no significant
changes were observed in the nasal airways even at concentrations as high
as 52.4 micrograms/m3. These results are consistent with earlier findings
in which repeated instillation of endotoxin produced significant increases
in Vs in the epithelial lining of the pulmonary airways and demonstrate
that inhaled endotoxin may play a role in the increase in sputum and
chronic bronchitis reported for workers exposed to organic dusts.
