Nitrite in saliva increases gastric mucosal blood flow and mucus thickness

Abstract

Salivary nitrate from dietary or endogenous sources is reduced to nitrite by oral bacteria. In the acidic stomach, nitrite is further reduced to NO and related compounds, which have potential biological activity. We used an in vivo rat model as a bioassay to test effects of human saliva on gastric mucosal blood flow and mucus thickness. Gastric mucosal blood flow and mucus thickness were measured after topical administration of human saliva in HCl. The saliva was collected either after fasting (low in nitrite) or after ingestion of sodium nitrate (high in nitrite). In additional experiments, saliva was exchanged for sodium nitrite at different doses. Mucosal blood flow was increased after luminal application of nitrite-rich saliva, whereas fasting saliva had no effects. Also, mucus thickness increased in response to nitrite-rich saliva. The effects of nitrite-rich saliva were similar to those of topically applied sodium nitrite. Nitrite-mediated effects were associated with generation of NO and S-nitrosothiols. In addition, pretreatment with an inhibitor of guanylyl cyclase markedly inhibited nitrite-mediated effects on blood flow. We conclude that nitrite-containing human saliva given luminally increases gastric mucosal blood flow and mucus thickness in the rat. These effects are likely mediated through nonenzymatic generation of NO via activation of guanylyl cyclase. This supports a gastroprotective role of salivary nitrate/nitrite.

NO generation from inorganic nitrate and nitrite: Role in physiology, nutrition and therapeutics

“…In addition to acting on luminal bacteria, nitrite-derived NO also affects the host mucosa. We now know that it stimulates gastric mucosal blood flow and mucus formation, and it reduces epithelial leakage; the three dominant mucosal defense mechanisms against luminal aggressors (Bjorne et al, 2004;Petersson et al, 2007). In animal experiments it has been shown that stimulation of gastric NO via ingestion of nitrate pro- Fig.…”

Proanthocyanidins in Buckwheat Flour Can Reduce Salivary Nitrite to Nitric Oxide in the Stomach

“…The results in this study also suggests that the concentration of NO in the stomach might increase if foods that contain ProA are ingested. The enhanced production of NO in the stomach may contribute to the increase in the activity of the stomach [32] helping the digestion of proteins in the stomach. On the other hand, ProA has been reported to be able to inhibit the digestion of starch and lipids in the intestine and the inhibition has been discussed in relation to the improvement of the glycemic index [33].…”

Physiological recycling of endogenous nitrate by oral bacteria regulates gastric mucus thickness

“…An increasing amount of studies are reporting protective and preventive NO-dependent effects of dietary nitrate and nitrite on cardiovascular, inflammatory and gastrointestinal diseases [9][10][11] . In fact, emerging data now suggest overall beneficial roles for these anions as opposed to the presumed association with gastrointestinal cancer and other diseases [12][13][14] , and these compounds clearly have profound effects on gastrointestinal functions 11,15,16 .…”