A phylogenetic study on the occurrence and distribution of histamine in the gastro-intestinal tract and other tissues of man and various animals.

ABSTI~.CT Using a specific fluorimetric and biological method, the occurrence and distribution of histamine was investigated in man, various mammals, birds, reptiles, amphibians, bony and cartilaginous fishes, lancelets, tunicates, echinoderms, molluscs, and crustaceans. The anune was identified by. the fluorescence spectrum, by specific antihistaminics in the bioassay, by the comparison of the fluorimetric histamine values following three different isolation procedures, and in some dssues also by thin-layer chromatography. Histamine was found in all chordates in considerable concentrations with the exception of the stomachiess carp. The distribution of histamine in the body, however, varied largely from species to species. Only the gastric mucosa of adl vertebrates investigated was relatively rich in histamine. The amine was nearly uniformly distributed in amphibians and fishes, in which only the stomach and partly the intestinum showed highdr histamine concentrations than all the numerous other tissues investigated. The distribution of histamine, however, in mammals, birds, and reptiles showed great variations from tissue to tissue. Organs free from histamine were first found in fishes going backward in the phylogeny. Because of the great variabilities in the distribution of histamine in the body of numerous species which were studied in this investigation, only one hypothesis can be developed with respect to a common physiological significance of histamine: there is a selective accumulation of histamine in the gastric mucosa of all chordates possessing acidsecreting cells and a low concentration of histamine in the gastro-intestinal tract of stomachless fishes. The gastric acid secretion is stimulated by histamine in all vertebrates investigated, whereas in many fishes histamine has no effects on the circulation or on smooth muscles of the gastro-intestinal tract or on the uterus. Thus, stored histamine probably has a specific function in the gastric mucosa, but not a general function, such as the regulation of ubiquitous metabolic processes or the regulation of microcircutation.