Autacoid and autonomic reactivity of bovine and ovine bronchus: modifications by antigenic sensitization.

Spirally cut bronchial strips, prepared from three bovine (horse plasma-sensitized calves, control calves and adult cattle) and two ovine (horse plasma-sensitized and control sheep) animal groups were studied in isolated organ baths and their responses to standard autacoid and autonomic agents were compared. All bovine preparations contracted to carbachol greater than 5 HT greater than histamine and relaxed to isoproterenol greater than adrenaline greater than phenylephrine. Responses of ovine bronchus to the above agonists were similar to bovine except to histamine which caused relaxations. Atropine antagonized carbachol-induced contractions while the relaxant responses of bronchial strips to isoproterenol and adrenaline were inhibited by propranolol in both ruminant species. Contractile effects of histamine were sensitive to mepyramine whereas cimetidine inhibited histamine-induced relaxations of ovine bronchus. The bronchial strips prepared from horse plasma-sensitized calves and sheep exhibited a significant (p less than .05) hyperreactivity to carbachol. The relaxant responses of sensitized calf bronchus to isoproterenol and adrenaline were also significantly (p less than .05) impaired when compared with respective controls. It is concluded that hypersensitization with foreign antigens might exaggerate the airway reactivity by rendering them hyperreactive to spasmogenic and hyporeactive to spasmolytic stimulation.