Clinical ResearchDietary nitrate generates potentially mutagenic concentrations of nitric oxide at the gastroesophageal junction☆,☆☆
Section snippets
Nitric oxide sensor
It was necessary to construct a sensor that would allow real-time in situ measurement of local concentrations of nitric oxide within the upper gastrointestinal tract. This was performed in collaboration with World Precision Instruments and was a modification of their standard laboratory nitric oxide sensor (ISO-NOP; World Precision Instruments, INC., Sarasota, FL). The sensor consists of a stainless steel canula containing an electrode that produces a current when exposed to nitric oxide. The
In vitro assessment of nitric oxide sensor
The custom-made nitric oxide sensor gave a linear response up to a nitric oxide concentration of 100 μmol/L. The sensor also showed a rapid response to changes in concentration of nitric oxide. On placing the sensor in a solution at 37°C containing 40 μmol/L nitric oxide, 80% maximal response was recorded within 10 seconds. On transferring it to a nitric oxide–free solution, 80% maximal resolution was recorded within 10 seconds.
The simultaneous measurement of nitric oxide in the solution in
Discussion
This study confirms previous reports that the nitrite present in saliva is converted to nitric oxide on entering the acid stomach.13, 14, 15, 16 By using a novel nitric oxide probe, we have extended previous work by showing that the highest nitric oxide concentrations generated in the gastric lumen occur at the gastroesophageal junction and cardia where saliva first meets acidic gastric juice.
The original report of luminal intragastric production of nitric oxide from salivary nitrite was by
Acknowledgements
The authors are grateful to Dr. Aled Evans and colleagues in the Department of Clinical Physics and Bio-Engineering, Southern General Hospital, Glasgow for their technical support.
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Address requests for reprints to: Kenneth E. L. McColl, M.D., University Department of Medicine & Therapeutics, Western Infirmary, Glasgow, G11 6NT Scotland. e-mail: [email protected]; fax: 0141 211 2895.
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This study was supported by a grant from the Biomedical and Clinical Research Committee of the Chief Scientist Office, Scottish Home and Health Department.