A study of bronchial responsiveness to inhaled cotton bract extracts (CBEs) was conducted. Thirteen healthy volunteers, nine males, 18 to 35 years old, underwent bronchoprovocation with 1 to 320 milligrams per milliliter (mg/ml) methacholine. Twenty four to 48 hours later they were exposed to an aqueous aerosol of CBE or normal saline solution (NSS). They underwent further CBE or NSS exposure and methacholine challenge 2, 8, and 24 hours and 7 days later. Pulmonary function was performed before and after each methacholine challenge. The effects on bronchial responsiveness were assessed by determining the methacholine concentration required to reduce maximal expiratory flow at 40 percent forced vital capacity on the partial expiratory flow volume curve (MEF40) by 25 percent (PC25). The CBE exposures induced a mean decrease in MEF40 of 23.5 percent that occurred 75 minutes after inhalation. NSS induced a decrease of 12.2 percent that occurred 1 minute after inhalation. CBE induced a transient decrease in MEF40 after methacholine challenge, the maximum decrease occurring 2 hours after inhaling CBE. The PC25 was 25.75mg/ml. The authors conclude that inhaling an aerosol of aqueous CBE causes a mild transient increase in responsiveness to methacholine challenge in healthy volunteers.
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