Related Experiment Videos
Mucous cell metaplasia in the airways of rats exposed to machining fluids
1Institute of Environmental Medicine, New York University Medical Center, Tuxedo, New York 10987, USA.
Abstract:
Occupational exposure to microbial-contaminated machining fluids is associated with a variety of adverse pulmonary effects including chronic bronchitis and increased sputum production. We have previously demonstrated in F344 rats that inhaled endotoxin can increase the amount of stored intraepithelial mucosubstances (Vs) in the respiratory tract. The purpose of the present study was to examine the effect of endotoxin-contaminated machining fluid aerosols on mucous production. Rats were exposed to aerosols of pyrogen-free water, 1 or 10 mg/m3 used machining fluid, or 10 mg/m3 unused machining fluid for 3 hr/day for 3 days. Twenty-four hours after the final exposure, right lung lobes were lavaged and the nasal cavity and left lung were fixed in formalin. The amount of Alcian blue/periodic acid-Schiff-stained mucosubstances was determined by morphometry. Exposure to 10 mg/m3 used machining fluid (equivalent to 0.8 micrograms/m3 endotoxin) produced a significant increase in Vs in the epithelial lining of both the nasal septum and intrapulmonary airways. These changes in Vs were accompanied by a significant increase in total cells and neutrophils in the lavage fluid. No changes in stored mucosubstances or lavage parameters were found in animals exposed to 1 mg/m3 used machining fluid aerosols. A significant increase in Vs was observed in the nasal septum but not in the intrapulmonary airways of animals exposed to 10 mg/m3 unused machining fluids (no measurable endotoxin). These results suggest that in addition to endotoxin, nonendotoxin components of machining fluids may contribute to the increase in sputum and chronic bronchitis reported for workers exposed to machining fluid aerosols.
Insights
Occupational exposure to machining fluid aerosols increases respiratory mucous production, particularly from endotoxin components. Non-endotoxin elements also contribute to airway inflammation and mucus, suggesting complex effects on lung health.
Area of Science:
- Toxicology
- Pulmonary Medicine
- Occupational Health
Background:
- Occupational exposure to microbial-contaminated machining fluids is linked to pulmonary issues like chronic bronchitis and increased sputum.
- Previous research showed inhaled endotoxin elevates stored intraepithelial mucosubstances (Vs) in the respiratory tract.
Purpose of the Study:
- To investigate the impact of endotoxin-contaminated machining fluid aerosols on mucous production in rats.
Main Methods:
- Rats inhaled aerosols of pyrogen-free water, used machining fluid (1 or 10 mg/m³), or unused machining fluid (10 mg/m³) for 3 hours daily over 3 days.
- Mucosubstance levels (Alcian blue/periodic acid-Schiff-stained) were quantified using morphometry.
- Lung lavage fluid was analyzed for cell counts (total cells and neutrophils).
Main Results:
- Exposure to 10 mg/m³ used machining fluid (0.8 µg/m³ endotoxin) significantly increased mucosubstances in the nasal septum and intrapulmonary airways.
- This increase in mucosubstances correlated with higher total cells and neutrophils in lavage fluid.
- Exposure to unused machining fluid (no measurable endotoxin) also raised mucosubstances in the nasal septum, but not intrapulmonary airways.
Conclusions:
- Endotoxin in machining fluids significantly contributes to increased respiratory mucosubstances and airway inflammation.
- Non-endotoxin components of machining fluids may also play a role in the pulmonary effects observed in exposed workers.
- Findings suggest a multifactorial basis for chronic bronchitis and sputum production associated with machining fluid exposure.