Response of the adrenergic system after provoked bronchoconstriction in patients with bronchial asthma.

Abstract

Objective:In this paper, effect of the Tolazoline as antagonist of the alpha-2 adrenergic receptors in patients with bronchial asthma and chronic obstructive bronchitis was studied, and also the effect of stimulation with Hexoprenaline of beta-2 adrenergic receptor after bronchi-constriction caused with Propranolol, and Acetylcholine.Methods:Lung function parameters are determined with Body plethysmography. In patients with bronchial asthma and chronic obstructive bronchitis was registered resistance (Raw), was determined the amount of intrathoracic gas volume (ITGV), and specific resistance was calculated as well (SRaw). Aerosolization was done with standard aerosolizing machine-Asema.Results:The study included a total of 21 patients. Two hours after the inhalation of Propranolol, in experimental group, it was applied the blocker of alpha-2 adrenergic receptors (Tolazoline 20 mg / ml with inhalator ways), which did not cause changes in bronchomotor tonus of tracheobronchial system (p > 1.0). Meanwhile, at the same patient, stimulation of beta-2 adrenergic receptor with Hexoprenaline (2 inh x 0.2 mg) is associated with a significant decrease of the specific resistance of airways (SRaw, p < 0.01). Control group results show that after bronchi-constriction caused by Propranolol-aerosol (20 mg / ml) in patients with bronchial asthma and chronic obstructive bronchitis, an increase of specific resistance in airways was caused (SRaw, p < 0.01), which confirms the presence of hyper-reactive bronco-constrictor effects intermediated by vagal ways. Two hours after Propranolol, inhaled Hexorenaline has blocked the action of Propranolol, but not entirely. Furthermore, two hours after acetylcholine-aerosol (1 mg /ml) was applied, inhaled Ipratropium (2 inh x 1 mg) has fully blocked the action of chemical bronchoconstrictor mediators, causing a decline of specific resistance in the airways (SRaw; p < 0.01).Conclusion:This suggests that primary mechanism, which would cause reaction in patients with increased bronchial reactibility, is prevalence of the cholinergic system over adrenergic one, and not the relationship in between alpha-2 and beta-2 adrenergic receptors.