Bronchial reactivity to histamine in young male smokers

Bronchial reactivity to inhaled histamine was determined in 17 non-asthmatic young male smokers and 21 non-smokers who were free of airflow obstruction. The 2 groups were similar in forced expiratory volume, maximal expiratory flow at 50% and 25% of vital capacity, slope of phase III of the single-breath nitrogen test (delta N2/l) and closing volume (CV/VC%). Bronchial reactivity was determined as PC20, provocation concentration reducing FEV1 by 20%, threshold concentration reducing FEV1 by two standard deviations, percentage reduction in FEV1 with histamine 16 mg/ml. Similar numbers of smokers and non-smokers had a PC20 below 16, 32 and 64 mg/ml. Threshold concentrations were the same in smokers and non-smokers, as was the reduction in FEV1 with histamine 16 mg/ml. The bronchoconstrictor response to histamine was significantly related to baseline measurements of expiratory flow (particularly in non-smokers), but not to delta N2/l or CV/VC%. Bronchial reactivity to histamine is not increased in young male smokers with normal lung function. The abnormal reactivity seen in older smokers is acquired, either from prolonged exposure to cigarette smoke itself, or resultant airway narrowing.