Changes in histamine and cyclic nucleotide levels after bronchoprovocation in patients with extrinsic asthma

The contents of histamine and cyclic nucleotides were studied in leukocytes before and after a bronchoprovocation test on patients with extrinsic asthma. The bronchospastic response correlated significantly with the reduction of the amount of histamine in leukocytes isolated after the provocation. The leukocytes cyclic AMP and cyclic GMP contents were slightly reduced after the provocation, while the plasma level of cyclic AMP was markedly increased. The beta-adrenoceptor response was tested on leukocytes, before the provocation. A normal elevation of the cyclic AMP content was obtained when the leukocytes were stimulated with isoprenaline, but after the provocation, isoprenaline had no significant effect. Only when a phosphodiesterase inhibitor was present did isoprenaline increase the cyclic AMP level in the postprovocation tests. It is suggested that the mediator release from the immunologic target cells is of importance for the bronchospastic response and that a desensitization of the beta-adrenoceptors of these cells is evident after bronchoprovocation.