Anaphylactic hypersensitivity in sheep lung in vitro: (vascular Schultz-Dale response and bioamine liberation).

Two aspects of anaphylactic hypersensitivity in sheep lung were studied. Isolated pulmonary vein constricted in response to histamine, acetylcholine, dopamine and bradykinin, whereas serotonin or specific antigen in sensitized tissue caused relaxation of the vessel. Tryptaminergic antagonists did not inhibit vessel relaxation caused by either serotonin or antigen. Antigenic challenge of chopped sheep lung caused significant liberation of serotonin and dopamine but not of histamine. It is suggested that anaphylactic release of serotonin may counteract the inflammatory response in sheep lung; which may explain the relative resistance of sheep to pulmonary hypersensitivity and tryptamine toxicity compared with other species.