[The effect of azelastine on the down-regulation of beta-adrenoceptors]

The effect of azelastine, a new on the down-regulation of beta-receptor agonist was investigated. Male Hartley guinea pigs received injections of saline or terbutaline (T.) and/or azelastine (A.) for successive 7 days. The radioligand binding assays for beta-adrenoceptors in the lung membranes of the guinea pigs were performed. The results showed the differences of numbers of maximal binding sites (Bmax) among four groups were significant. The Bmax of beta-adrenoceptor in T. group was less than that in control group (P less than 0.02). The Bmax in A. group was more than that in control group (P less than 0.05). The Bmax in T. plus A. was more than that in T. group, and there was no significant difference between Bmax in T. group and in T. plus A. group (P greater than 0.1). The differences of affinity (Kd) of beta-adrenoceptor among four groups were not significant. Azelastine increased the density of beta-adrenoceptors and partially prevented the down-regulation of beta-adrenoceptor caused by terbutaline.