Experimental canine anaphylaxis: cyclic nucleotides, histamine, and lung function

We studied the effects of Ascaris suum antigen (iv) in 32 natively allergic, anesthetized dogs. After thoracotomy, bilateral cervical vagotomy, and propranolol, samples of peripheral lung frozen in situ were obtained for measurement of cyclic nucleotides and histamine. Following Ascaris, lung histamine decreased 20.4 +/- 3.7% (mean +/- SE), cAMP increased 391 +/- 122%, and cGMP increased 110 +/- 20% with increased plasma histamine and physiological changes of anaphylaxis. No significant changes occurred in 10 control dogs. Release of histamine, reflecting immunological degranulation of mast cells, correlated closely with the physiological effects of anaphylaxis. beta-Adrenergic stimulation with isoproterenol prevented these physiological effects of anaphylaxis in three dogs studied. Furthermore, the level of cAMP induced in lung tissue by beta-adrenergic stimulation in these dogs correlated with the degree of inhibition of immunologically induced histamine release. These results illustrate the suitability of this experimental preparation to study the biochemical and physiological mechanisms of anaphylaxis in vivo.