Effect of Free Dietary Glutamate on Gastric Secretion in Dogs

Abstract

The amino acid, L-glutamate, which is abundant in many foodstuffs, is a potent stimulator of gastric vagal afferents. The aim of the study was to evaluate a role of dietary glutamate in neuroendocrine control of gastric secretion of acid, pepsinogen, and fluid. In mongrel dogs with small gastric pouches surgically prepared according to Pavlov (vagally innervated) or Heidenhain (vagally decentralized), secretion in a pouch was induced by infusion into the main stomach of an amino acid-rich diet lacking glutamate (Elental) or the same diet supplemented with monosodium glutamate (MSG). Having no effect alone, MSG (100 mM) potentiated secretion induced by Elental both in Pavlov and Heidenhain models. In the Pavlov pouch, the effect of MSG was markedly reduced after i.v. injection of granisetron, an antagonist of 5-HT(3) receptors. In the Heidenhain model, MSG enhanced the stimulatory effect of pentagastrin (1 microg/kg, s.c.). In conclusion, dietary glutamate at doses not exceeding its common concentrations in foods substantially potentiates gastric phase secretion induced by stimulation of gastric mucosa with an amino acid-rich diet or by administration of pentagastrin. The effect of glutamate is partially mediated via serotonin secretion and stimulation of 5-HT(3) receptors.

EAAT3 promotes amino acid transport and proliferation of porcine intestinal epithelial cells

“…Glu absorption is mainly mediated by EAAT3 in the nervous system [16], gastrointestinal tract [5, 17] and skeletal muscle [18]. Our previous studies revealed that EAAT3 is a marker of intestinal growth during embryonic development in chicks [7, 19] and pigeons [20–22].…”

Nutritional and Physiological Significance of Luminal Glutamate-sensing in the Gastrointestinal Functions

“…In this experiment, we examined the eŠect of free glutamate on gastric acid secretion when injected directly into the main stomach of Pavlov pouch dogs. 40,41) We used an enteral liquid diet (Elental TM ) as a nutrient, which is mainly composed of a mixture of amino acids,ˆnal nutrients digested from protein.…”

Physiological Significance of Glutamate Signaling in Gut-Brain Communication

“…In support of this idea, adding MSG to an amino acid-rich diet (but not a glutamate diet) dosedependently potentiates secretion of acid, fluid and pepsinogen from vagally innervated ("Pavlov") small gastric pouches when nutrients are infused into the main stomach (isolated from the Pavlov pouch) of conscious dogs (63). These MSG effects are markedly reduced after intravenous injection of granisetron, an antagonist of 5-HT 3 R. Vagal decentralization ("Heidenhain" pouch) partly reduced the potentiating effects of dietary MSG.…”