ALLERGEN-INDUCED HYPERRESPONSIVENESS TO BRADYKININ IS MORE PRONOUNCEDTHAN THAT TO METHACHOLINE

Bradykinin reduces airflow in asthmatic patients via indirect mechanis m(s), possibly involving sensory nerve stimulation and increased vascu lar permeability. We hypothesized that allergen inhalation, which affe cts reactivity of nerves and vessels, would differentially alter react ivity to bradykinin and the smooth muscle spasmogen methacholine. We c ompared reactivity to methacholine and bradykinin 1, 2, 4, 7, 11, and 14 days after allergen provocation in 12 atopic asthmatic patients wit h stable baseline reactivity to bradykinin. Maximal allergen-induced s hifts from baseline in reactivity were 0.73 +/- 0.12 log unit for brad ykinin compared with 0.27 +/- 0.13 log units for methacholine (P = 0.0 005). Nine subjects showed significant increases in bradykinin reactiv ity, with four subjects increasing reactivity by >1 log unit. Moreover , the maximal mean change in bradykinin reactivity occurred 2 days pos tallergen. Thus, allergen-induced changes in reactivity to bradykinin and methacholine differ in magnitude and time course. Bradykinin inhal ational challenge provides a sensitive index of the airway's response to allergen.