Biogenesis of histamine.

The origin of histamine bound in certain mammalian tissues, in which it is available for release in such conditions as tissue damage and anaphylactic shock, has not been conclusively demonstrated. It has been postulated that it arises either from dietary histidine or from exogenous histamine formed in the intestine or in tissues high in histidine decarboxylase (1). Increases, of brief duration, in the histamine content of guinea pig urine and lung have been reported to follow administration of large amounts of histidine (2, 3), but, when smaller quantities of histidine were injected, no increase of histamine could be demonstrated in urine. In this paper it is shown that, following a small dose of radioactive L-histidine, radioacti,ve histamine can be detected in the urine and in certain internal organs for many days. In contrast, after administration of C14-histamine, none of this substance could be detected in the same internal organs after 4 hours.