Formation of amines in the gastric mucosa of the rat.

Abstract

HISTAMINE may have some role, as yet unknown, in the chemical regulation of gastric secretion1. This view is based on the effectiveness of histamine in producing acid secretion, on the presence of histamine in the gastric juice, and on the high concentration of histamine in the gastric mucosa of several species. The rich supply of histamine in this tissue in the rat is coincident with a high histidine decarboxylase activity2, probably indicating a local synthesis of the amine. Several animal tissues contain L-3,4-dihydroxyphenylalanine (DOPA) decarboxylase, which attacks all aromatic amino-acids, including 5-hydroxytryptophan (5-HTP) and histidine3–5. This enzyme, however, decarboxylates histidine only inefficiently and the physiological significance of this aspect of its function remains uncertain3,6. Another more specific histidine decarboxylase has been demonstrated in the foetal rat7,8 and in the bone marrow of the adult rat9. In a recent investigation DOPA decarboxylase, as well as the specific histidine decarboxylase (cf. Weissbach et al.3), were demonstrated in the gastric mucosa of the rat10. While the presence of specific histidine decarboxylase seems to account for the formation of gastric histamine and ultimately for the postulated control of gastric secretion, the physiological significance of a high gastric DOPA decarboxylase activity is unknown.