Histamine in the tissues of the marsupial Setonix brachyurus (the quokka).

Passive cutaneous anaphylactic (PCA) reactions in the marsupial Setonix brachyurus (the quokka) were completely inhibited by the histamine antagonist mepyramine maleate, but were unaffected by disodium cromoglycate or the serotonin antagonist, methysergide. Histological examination of quokka skin indicated that mast cell degranulation occurred during the PCA reaction in this marsupial and animals whose skin was relatively deficient in mast cells were poor PCA recipients. In contrast to many eutherian (placental) species, this marsupial was found to lack histamine in blood leukocytes and platelets. Also, while the peritoneal mast cells of rats and mice contain large quantities of histamine, this amine was not detected to quokka peritoneal washings, even after the induction of a peritoneal exudate or the regular intraperitoneal injection of antigen. Immunologic challenge of quokka blood or peritoneal cells did not induce the synthesis of histamine, but histamine release was elicited from sensitized quokka lung by antigenic challenge.