Modulation of beta 2-adrenoceptors in human lymphocytes by in vitro stimulation with mediators

Since Szentivanyi established the beta-adrenergic theory, many attempts have been made to explain the dynamics of bronchial hyperreactivity and cytotropic allergic reaction by this mechanism. In previous work, we found that beta-adrenoceptor numbers were decreased in symptomatic patients and after specific antigenic exposure. As a result, we postulated that this might be due to mediator activity. Blood was extracted from 46 healthy donors for this study. Radioligand [125I]-iodocyanopindolol was used for beta-adrenoceptor determination in peripheral blood lymphocytes following Brodde's method. Student's t test was used for statistical analysis. beta-Adrenoceptor number was determined before and after exposure to mediators (histamine, PAF, LTD4), and after melittin (phospholipase A2, PLA2, activator) exposure. A significant decrease was obtained after histamine (p < 0.05), LTD4 (p < 0.05) and melittin (p < 0.001) exposure; PAF did not modify the number of beta-adrenoceptors. In conclusion, our results confirm that down-regulation of beta-adrenoceptors can be induced by mediator release.