Saliva has a high nitrite content derived from the enterosalivary recirculation of dietary nitrate.
When the saliva meets acidic gastric juice, the nitrite is converted to nitrous acid, nitrosative species, and nitric oxide.
In healthy volunteers this potentially mutagenic chemistry is focused at the gastric cardia.
Professor McColl and colleagues from Scotland studied the location of this luminal chemistry in Barrett's patients during acid reflux.
The research team studied 10 Barrett's patients before and after administration of 2 mmol nitrate.
Using microdialysis probes the team measured nitrite, ascorbic acid, and total vitamin C.
|Acid reflux generates up to 60 µM nitric oxide within the Barrett's segment |
The team also measured thiocyanate concentrations and pH simultaneously in the proximal esophagus, Barrett's segment, and hiatal sac.
The proximal stomach, and distal stomach were also measured using the probes.
In a subgroup, real time nitric oxide concentrations were measured.
During acid reflux, the team noted that Barrett's segment was the anatomical site with maximal potential for acid catalysed nitrozation.
The researchers observed that Barrett's segment had a median concentration of nitrite exceeding that of ascorbic acid in 2 of 10 subjects before nitrate.
However, Barrett's segment had a median concentration of nitrite exceeding that of ascorbic acid in 4 of 9 after nitrate.
The researchers noted that thiocyanate, which catalyzes acid nitrosation, was abundant at all anatomical sites.
On entering the acidic Barrett's segment, there was a substantial fall in nitrite and the lowest ascorbic acid to total vitamin C ratio.
The team reported that this was indicative of reduction of salivary nitrite to nitric oxide at this anatomical site.
Episodes of acid reflux were observed to generate nitric oxide concentrations of up to 60 µM within the Barrett's segment.
Professor McColl's team concluded, “The interaction between acidic gastric refluxate and nitrite rich saliva activates potentially mutagenic luminal nitrozative chemistry within Barrett's esophagus.”