Spontaneous argyrophil cell carcinoid in the glandular stomach: immunohistochemical study of gastric endocrine cells in normal and tumour-bearing mastomys.

Endocrine tumours (argyrophil cell carcinoids) are frequent in the oxyntic mucosa of mastomys. The tumour is notable for its high histamine content and for its high histidine decarboxylase activity. The tumour is thought to arise from the histamine-storing, enterochromaffin-like cells of the oxyntic mucosa. They are of two ultrastructurally distinguishable types, ECL cells and A-like cells, both of which have been demonstrated in the tumour. Identical cells have been demonstrated in the oxyntic mucosa of the rat; there is much evidence that in this species the functional activity and the number of these cells are determined by the serum gastrin concentration. However, tumours have never been found to arise from these cells in the rat. As an initial step in an attempt to explain the formation of the gastric endocrine tumour in the mastomys we examined the distribution and frequency of occurrence of endocrine cells in the mastomys stomach. Gastrin cells in the antrum of mastomys seemed to occur in about the same frequency as in the antrum of rat and mouse. 5-HT-storing enterochromaffin cells, however, were considerably more numerous in the mastomys, whereas the somatostatin cells in the antrum were fewer. The number of enterochromaffin-like cells and somatostratin cells in the oxyntic mucosa of mastomys was much lower than in the rat and mouse. Once developed, the gastric endocrine tumour seems to reduce the antral gastrin cell number; the larger the tumour the greater the reduction.