Airway responses to the inhalation of cotton dust and cotton bract extracts.

BACKGROUND

Exposure to dust in the cotton industry is associated with respiratory dysfunction. Healthy subjects challenged with cotton bract extract (CBE) develop transient airway hyperresponsiveness. CBE, a major component of cotton dust, is potentially an important agent for studying byssinosis.

OBJECTIVES

To compare airway responses to cotton dust extract (CDE) and CBE in healthy subjects.

METHODS

In 21 healthy, non-smoking subjects we compared the effects of CBE and CDE in a double-blind random order, following a 10-min aerosol inhalation. The response to methacholine (MCh) 2 h following CBE or CDE was measured. Lung function was recorded using maximal (MEFV) and partial expiratory flow volume (PEFV) curves, measuring MEF at 60% of baseline vital capacity below total lung capacity [MEF40%(P)] on the PEFV curve. Responders were subjects who developed a 20% or greater fall in MEF40%(P) following extract challenge. Endotoxin levels were low for CBE (5.71 EU/mg) and CDE (31.88 EU/mg).

RESULTS

There were 18 responders to CBE and 17 responders to CDE. The average maximal falls in MEF40%(P) were 70 +/- 4.9 and 70 +/- 4.4% of baseline (nonsignificant) following CBE and CDE, respectively. All subjects enhanced their MCh response following CBE or CDE. The MCh dose which reduced MEF40%(P) by 40% was identical for CBE and CDE (1.3 microg/ml).

CONCLUSIONS

We conclude that CBE and CDE exert similar physiologic effects.