β-Adrenoceptor desensitization induced by antigen challenge in guinea-pig trachea

As β-adrenoceptor function in the lung could be relevant in asthma, we carried out a functional and biochemical study of the possible occurrence of β-receptor desentization after the anaphylactic reaction induced in vitro in actively sensitized guinea-pig tracheas. The relaxing effect of epinephrine and vasoactive intestinal polypeptide (VIP) was tested in tracheal strips. Binding was studied with tracheal membranes and 125I-cyanopindolol. Antigen challenge resulted in a marked decrease of epinephrine-induced relaxation paralleled by a 50% reduction in β-receptor number. The adrenergic system was specifically affected since VIP-induced relaxation was not modified by the anaphylactic reaction. In some experiments tissues were pretreated with hydrocortiosne or indomethacin. Both these drugs prevented antigen exposure from impairing epinephrine relaxation, suggesting the involvement of eicosanoids in this phenomenon. Our data clearly indicate the occurrence of β-receptor desensitization as a consequence of the anaphylactic reaction, thus impairment of the adrenergic system might play a role in asthma.