Related Experiment Video
Updated: Sep 26, 2026

Preparation of Rat Skeletal Muscle Homogenates for Nitrate and Nitrite Measurements
Published on: July 29, 2021
Studies of nitric oxide generation from salivary nitrite in human gastric juice
K Iijima1, V Fyfe, K E L McColl
1Dept. of Gastroenterology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
Background:
Saliva contains substantial concentrations of nitrite derived from the enterosalivary recirculation of dietary nitrate.
Methods:
We have investigated factors in gastric juice influencing the fate of nitrite in swallowed saliva. When nitrite (100 microM) is added to human gastric juice pH 1.5 or pH 2.5 at 37 degrees C containing physiological concentrations of thiocyanate (1 mM) and ascorbic acid (200 microM), it is converted to nitric oxide within a few seconds.
Results:
The reduction of nitrite to nitric oxide is slower at pH 3.5 and very little is generated at pH 4.5. The rate of nitric oxide generation at acid pH increases with increasing thiocyanate concentration. The concentration of nitric oxide generated in the above way is maintained until the ascorbic acid is depleted by the recycling of nitric oxide to nitrite. In gastric juice depleted of ascorbic acid, very little nitrite is reduced to nitric oxide at any pH.
Conclusion:
These studies indicate that in the healthy acid-secreting stomach most salivary nitrite will be reduced to nitric oxide at the gastro-oesophageal junction and gastric cardia where it first encounters gastric juice.
Related Concept Videos
Nitric Oxide Signaling Pathway
2° Amines to N-Nitrosamines: Reaction with NaNO2
Overview of Human Digestion
Inorganic Nitrogen Assimilation
Stomach pH Regulation
The acid-secreting gastric mucosal epithelial cells (parietal cells) lining the stomach lumen maintain the low pH in the lumen. Numerous ion transporters and channels on these parietal...
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by water loss...

