Cotton Bract and Acute Airway Constriction in Humans

Abstract

On Monday or on the first work day after an absence, cotton textile workers experience acute symptoms of chest tightness, shortness of breath and cough accompanied by a decrease in FEV1.0, MEF40%(P), and other pulmonary function parameters indicative of airway narrowing. This response to inhaling cotton dust, which characterizes the early stages of byssinosis, can be reproduced in the laboratory by inhalation challenge of healthy human volunteers with aqueous extracts of cotton bracts(1g bracts/6 ml H2O). Bracts (the leaf-like structures surrounding the stem of the cotton boll) are a major component of the mill dust. On first exposure to bract extract, 60% of our volunteers responded with decreases in FEV1.0 of 5% or greater and corresponding MEF40%(P) decreases of 20% or greater. The response was reproducible in subsequent challenges delayed one week or longer. None of our volunteers had ever had a previous exposure to cotton dust. The causative agent(s) is not known. We have used inhalation challenge in volunteers who are responders as a bioassay for detection of airway constrictor activity in purified bract extracts. Crude aqueous extracts contain 60 mg dry weight material per milliliter. Precipitation of protein by methanol, removal of anions by DEAE chromatography, and extraction with ether reduces the dry weight material to 10 mg/ml and this purified extract retains 70% of its original airway constrictor activity. Tests are positive for the presence of sugars and amino nitrogen. Size exclusion chromatography has shown that airway constrictor activity is associated with the less than 1,000 molecular weight fraction.