Amine mechanisms in enterochromaffin and enterochromaffin-like cells of gastric mucosa in various mammals.

Abstract

The stomach wall from a variety of mammals (mouse, rat, hamster, guinea-pig, rabbit, cat, dog, pig, monkey and man) was analyzed histochemically and chemically for the presence of histamine, arylethylamines and the corresponding amino acid decarboxylases. 1. Apart from adrenergic nerve terminals, the major cellular stores for gastric amines were mast cells, enterochromaffin cells, and a system of morphologically similar cells designated as enterochromaffin-like cells. 2. Using the histochemical o-phthaldialdehyde technique, histamine could be visualized in gastric mast cells from all species. In addition, a yellow formaldehyde-induced fluorescence indicating the presence of 5-hydroxytryptamine or some other indole, was found in the gastric mast cells from mice, rats, rabbits, cats, dogs, pigs and monkeys. In hamsters the mast cells exhibited a green colour rather indicating the presence of a catecholamine. 3. All argyrophilic epithelial cells in the stomach mucosa emitting a formaldehyde-induced fluorescence were classified as enterochromaffin. Yellow-fluorescent, presumably 5-hydroxytryptamine-containing, enterochromaffin cells were recognized in all species. In addition, the stomach mucosa of rabbits and cats contained scattered green-fluorescent enterochromaffin cells; in microspectrofluorometric analysis the fluorophore was identified with the formaldehyde condensation product of dopamine. The presence of dopamine in gastric mucosa of these two species was further confirmed by chemical estimation in combination with thin-layer chromatography. 4. Already the presence of different arylethylamines in the enterochromaffin cells indicates the existence of several distinct cell types. A further classification was made on the basis of a different sensitivity to the amine-depleting action of reserpine. 5. The enterochromaffin-like cells are argyrophil but not argentaffin. A distinguishing feature of these cells is their ability to produce and store arylethylamines, such as dopamine, upon administration of the amine precursor (e.g.l-DOPA), although normally the cells are devoid of fluorogenic amines demonstrable with the formaldehyde method. In addition, the enterochromaffin-like cells of mouse and rat store histamine histochemically detectable with the o-phthaldialdehyde technique. In the mouse and rat these cells appear to be the major site of gastric histidine decarboxylase. In no other species could histamine or histidine decarboxylase be demonstrated in the enterochromaffin-like cells. 6. The regional distribution of the enterochromaffin and enterochromaffin-like cells varied markedly, but the localization of these two cell systems was characteristic for each species. It was very noticeable that the distribution of the cells within the gastric mucosa often was not limited to one or the other of the histologically definable glandular areas. 7. From observations on the regional and topographic distribution of DOPA decarboxylase (i.e. non-specific l-amino acid decarboxylase) it is suggested that the enzyme occurs in both enterochromaffin and enterochromaffin-like cells, in particularly high concentration in the former cell type. 8. The enterochromaffin and enterochromaffin-like cells — i.e. the entire system of gastric argyrophil cells — may have an endocrine function. It is evident that a thorough knowledge of the properties and distribution of the many types of cells comprising this system will assist in defining their respective endocrine mechanisms.