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Reduced beta 2-adrenoceptor responsiveness in exercise-induced asthma.
Chest
|October 1, 1985
Summary
Beta-2 adrenoceptor responsiveness is reduced in patients with exercise-induced asthma (EIA), but not in non-EIA asthmatics. This impairment was observed both in vivo and in vitro, potentially explaining research discrepancies regarding beta-adrenoceptor function in asthma.
Area of Science:
- Pulmonary Medicine
- Pharmacology
- Respiratory Physiology
Background:
- Asthma is a chronic respiratory disease characterized by airway inflammation and bronchoconstriction.
- Beta-adrenoceptor agonists are primary bronchodilators used in asthma management.
- Previous studies on beta-adrenoceptor function in asthma have yielded conflicting results.
Purpose of the Study:
- To investigate beta-adrenoceptor responsiveness in patients with exercise-induced asthma (EIA) compared to asthmatic patients without EIA (NEIA) and healthy controls.
- To determine if reduced beta-adrenoceptor function is specific to EIA.
- To explore potential reasons for discrepancies in the literature regarding beta-adrenoceptor function in asthma.
Main Methods:
- In vivo assessment of beta-adrenoceptor responsiveness using intravenous isoprenaline infusion and measuring plasma cyclic AMP and diastolic blood pressure.
- In vitro assessment of beta-2 adrenoceptor function by measuring isoprenaline-stimulated cyclic AMP accumulation in lymphocytes.
- Comparison of responses between age- and sex-matched groups: EIA, NEIA, and control subjects, all medication-free for at least one week.
Main Results:
- In vivo beta-2 adrenoceptor mediated responses to isoprenaline (decreased diastolic blood pressure, increased plasma cyclic AMP) were significantly reduced in EIA patients.
- In vitro beta-2 adrenoceptor mediated cyclic AMP accumulation in lymphocytes was attenuated in EIA patients.
- Beta-adrenoceptor responsiveness was normal in NEIA patients and control subjects, both in vivo and in vitro.
Conclusions:
- Beta-2 adrenoceptor mediated responses are impaired both in vivo and in vitro in patients with exercise-induced asthma.
- This selective reduction in beta-2 adrenoceptor responsiveness in EIA may contribute to the variability observed in previous asthma research.
- The findings suggest a specific defect in beta-2 adrenoceptor function in a subgroup of asthmatic patients (EIA).