Am. J. Respir. Crit. Care Med., Vol 151, No. 6, 06 1995, 1981-1988.
Cotton dust produces an increase in intraepithelial mucosubstances in rat airways
T Gordon and JR Harkema
Institute of Environmental Medicine, New York University Medical Center, Tuxedo 10987, USA.
Occupational exposure to endotoxin-contaminated organic dusts is associated
with a variety of adverse pulmonary effects, including chronic bronchitis
and sputum production. We have previously demonstrated in F344 rats that
inhaled endotoxin rapidly induces an increase in the volume of stored
intraepithelial mucosubstances (Vs) in the respiratory tract. The present
study examined whether endotoxin- contaminated cotton dust can produce a
similar increase in Vs in this animal model. Rats were exposed to air or
1.5 to 15.0 mg/m3 cotton dust for 2 h/d for 3 d. Twenty-four hours after
the final exposure, the nasal cavity and lungs were fixed in formalin and
the presence of Alcian blue/periodic acid-Schiff-staining mucosubstances
determined by morphometry. Exposure to cotton dust produced
concentration-dependent changes in Vs in the nasal septum and
intrapulmonary airways. Statistically significant increases in Vs were
observed in the epithelial lining of the nasal septum of animals exposed to
5.3 and 14.5 mg/m3 cotton dust (equivalent to 2.8 and 8.9 micrograms/m3
endotoxin). Vs in the intrapulmonary airways was also significantly
increased at these concentrations. No significant changes were observed in
the nasal septum or intrapulmonary airways after exposure to 1.8 mg/m3
cotton dust. These results are consistent with the hypothesis that
endotoxin may contribute to the increase in human cases of chronic
bronchitis reported in occupational settings in which endotoxin-
contaminated dusts are encountered.
