Effect of nitrite delivered in saliva on postprandial gastro-esophageal function.

OBJECTIVE: Acid reflux produces troublesome symptoms (heartburn) and complications including esophagitis, Barrett's esophagus, and adenocarcinoma. Reflux occurs due to excessive and inappropriate relaxation of the lower esophageal sphincter. An important mediator of this is nitric oxide, high concentrations of which are generated within the lumen when swallowed saliva meets gastric acid. Saliva contains nitrite, derived from the enterosalivary recirculation of dietary nitrate, which is reduced to nitric oxide by gastric acid. The aim of this study was to investigate whether salivary nitrite contributes to dysfunction of the lower esophageal sphincter. MATERIALS AND METHODS: In 20 volunteers, studies of gastro-esophageal function were performed on four separate days, following consumption of a standardized meal, with saliva nitrite concentrations modified differently each day by intra-oral nitrite infusion. RESULTS: The infusions produced an appropriate range in saliva nitrite concentrations, from below to well above the physiological range. The standardized meal induced expected physiological changes in gastro-esophageal function confirming the recordings were sensitive and robust. Esophageal acid exposure (primary outcome) was similar on each study day. Secondary outcomes, including number and duration of reflux events, rate of transient lower esophageal sphincter relaxations, lower esophageal sphincter pressure and rate of gastric emptying were also unaffected by variations in saliva nitrite concentration. CONCLUSIONS: Nitrite in swallowed saliva does not modify gastro-esophageal junction function or predispose to gastro-esophageal reflux. The wide range in saliva nitrite concentrations, the sensitivity of the physiological recordings and the number of subjects studied make it very unlikely that an effect has been missed.

Nitrogenous chemicals generated from acidification of saliva influence transient lower oesophageal sphincter relaxations.

OBJECTIVE: Saliva contains high concentrations of nitrite derived from the enterosalivary recirculation of dietary nitrate and its reduction by buccal bacteria. Acidic gastric juice converts the swallowed nitrite to varying proportions ofnitrous acid and nitric oxide (NO) depending upon ascorbic acid availability. Neuronally generated NO is the key in the pathway of transient lower oesophageal sphincter relaxations in vivo. Furthermore, in vitro NO and nitrous acid relax the smooth muscle of the stomach, lower oesophageal sphincter (LOS) and oesophageal body. The objective of this article was to determine whether luminal administration of NO or nitrous acid affects the generation of transient LOS relaxations following a meal. MATERIAL AND METHODS: Fifteen healthy subjects were studied on three separate days. A manometry catheter was used to record oesophageal, LOS and gastric pressures, and two oesophageal pH probes were used to record reflux. One of three solutions was infused each day into the cardia after a standardized meal: 1) control solution ofhydrochloric acid pH 1.0, 2) nitrous acid and 3) nitrous acid plus ascorbic acid to generate NO. The solutions were randomized and double-blinded. RESULTS: The frequency of transient LOS relaxations was increased by the NO-generating solution at 5.2/h compared with both the control (3.5, p <0.01) and nitrous acid solution (3.1, p <0.0001). The NO-generating solution also increased oesophageal acid exposure to 62.2%, compared with both the control (37.5%, p <0.03) and nitrous acid solution (36.6%, p <0.002). CONCLUSIONS: Luminal NO at the gastro-oesophageal junction increases the generation of transient LOS relaxations following a meal. Chemicals generated by the acidification of salivary nitrite may contribute to gastro-oesophageal motility disorders.