Effect of azelastine on the down regulation of beta-adrenoceptors in guinea pig lung.

The new antiallergic drug azelastine (E-0659, Azeptin; CAS 58581-89-8) is used in the treatment of rhinitis and bronchial asthma. In the present study, the effect of azelastine on the regulation of the beta-adrenoceptors and the down regulation of beta-adrenoceptors by terbutaline, a beta-agonist, was investigated using guinea pig lungs. Guinea pigs were divided into four groups; (1) the control (saline-treated) group, (2) the terbutaline-treated group, (3) the azelastine-treated group, (4) terbutaline plus azelastine-treated group. Guinea pigs intramuscularly injected with each agent three times a day for successive 7 days. In the terbutaline-treated group, a 26% reduction in the number of beta-adrenoceptors compared with those of the control group was observed. In the azelastine-treated group, the number of beta-adrenoceptors increased by 24% compared with those of the control group. The number of the beta-adrenoceptors in the terbutaline plus azelastine-treated group was significantly increased compared with that of the terbutaline-treated group. These results suggest that azelastine may prevent the down regulation observed during beta-agonist administration by increasing the number of beta-adrenoceptors.