Decrease of beta-receptors after the antigen-specific bronchial provocation test in bronchial asthma.

Airway hyperreactivity to different stimuli is a characteristic feature of bronchial asthma. The beta-adrenergic theory, as proposed by Szentivanyi in 1968, tried to explain with beta-adrenergic dysfunction, the cause not only of bronchial hyperreactivity but of all atopic diseases. In a previous work, we found that asymptomatic asthmatic patients presented a number of beta-receptors similar to that of a normal control group, while symptomatic asthmatic patients presented a significantly decreased number when compared to both groups (40% decrease). In view of these results, we proposed to study the possible changes in the number of beta-receptors in asymptomatic asthmatic patients after a bronchial provocation test. Fifteen patients, diagnosed of bronchial asthma and sensitive to the house dust mite, D. pteronyssinus, were studied. All were free of medication and asymptomatic at least 90 days before the study. A test of specific bronchial provocation was performed on 10 patients, determining the number of beta-receptors in basal conditions, after 30 minutes and 24 hours. The other five patients underwent an unspecific provocation test with methacholine, with determination of the beta-receptor number at basal conditions, and 24 hours later. Only a significant decrease (30.4%) was found in the beta-receptor numbers, 24 hours after specific bronchial provocation with p less than 0.025 with the Student test for paired data. With regards the beta-adrenergic theory of atopy, in our opinion our results show that the detected decrease of beta-receptors would be the consequence and not the cause of atopic diseases.