Gastric histamine metabolism and acid secretion in rats as influenced by diet and nutrient content.

Diets containing egg white, casein, menhaden fish meal, soy protein or wheat gluten were fed to rats to assess the impact of dietary protein (and other nutrients) on gastric functions. The menhaden fish meal group exhibited increases in stomach histidine decarboxylase (HDC) activity, histamine concentration, as well as acid secretion when compared with the control, casein group. When rats were fed amino acid-supplemented casein or fish meal diets to simulate each other's amino acid profile, a small increase in gastric HDC activity, histamine content and acid secretion was observed in comparison with the unsupplemented casein or fish meal groups. The high mineral content of menhaden fish meal (15%) was thought to be a potential inducing factor for gastric histamine metabolism and acid secretion. Adding fish meal ash to the casein diet or to a cod fillet diet elevated stomach HDC activity and histamine concentration significantly. Furthermore, when calcium (Ca) was added to the casein diet to simulate its high content in menhaden fish meal (7.8%), similar elevated levels of gastric histamine were obtained for the Ca-supplemented casein group as for the fish meal group. The role of Ca could be due to release of gastrin, which results in release of stomach histamine, or by facilitating mast cell histidine incorporation with subsequent histamine synthesis.