Beta-adrenoceptor desensitization in a model of experimental asthma in guinea-pigs

We have investigated the possible occurrence of the desensitization of pulmonary beta-receptors in a model of experimental asthma such as the ovalbumin sensitized guinea-pig. Although some differences such as the ovalbumin sensitized guinea-pig. Although some differences were observed between normal and asthmatic guinea-pigs, the desensitization procedure (isoproterenol (ISO) 10-6M x 20 min x 2) markedly impaired the relaxing capacity of ISO, epinephrine (EPI) and procaterol. Within the beta2 agonist procaterol, the sensitized tissues seemed to be more sensitive compared to normal. In parallel, the desensitization procedure produced a greater decrease in the relaxing capacity of procaterol in the sensitized tracheas. On the other hand, the two unselective beta-agonists (ISO and EPI) did not seem to discriminate between the two experimental conditions used. These data suggest that the immunological disturbance due to the active sensitization may induce a modification in beta-adrenoceptor reactivity. The results obtained with EPI after anaphylactic challenge are in agreement with this. In fact, the relaxing capacity of EPI was markedly reduced by antigen challenge.