MODULATION OF BETA-2-ADRENOCEPTORS IN HUMAN-LYMPHOCYTES BY IN-VITRO STIMULATION WITH MEDIATORS

Since Szentivanyi established the beta-adrenergic theory, many attempt s 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 postul ated that this might be due to mediator activity. Blood was extracted from 46 healthy donors for this study. Radioligand [I-125]-iodocyanopi ndolol was used for beta-adrenoceptor determination in peripheral bloo d 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 meli ttin (phospholipase A2, PLA2, activator) exposure. A significant decre ase was obtained after histamine (p < 0.05), LTD4 (p < 0.05) and melit tin (p < 0.001) exposure; PAF did not modify the number of beta-adreno ceptors. In conclusion, our results confirm that down-regulation of be ta-adrenoceptors can be induced by mediator release