The relationship between plasma and salivary NOx.

Area of Science:

• Biochemistry
• Physiology
• Cardiovascular Health

Background:

• Plasma nitrite (NO2(-)) reflects endothelial nitric oxide synthase (NOS) activity, but plasma nitrate (NO3(-)) and NOx do not.
• Dietary nitrate (NO3(-)) can increase plasma nitrite (NO2(-)) via oral bacteria and salivary reuptuptake.
• Salivary NO2(-) and NO3(-) are proposed as indicators of plasma NO levels and endothelial function, with commercial test strips available.

Purpose of the Study:

• To determine the correlation between salivary and plasma nitrite (NO2(-)) and nitrate (NO3(-)) levels in healthy adults.
• To assess if salivary NO3(-) reduction efficiency correlates with plasma NO2(-) and NO3(-) increases after beetroot juice consumption.

Main Methods:

• Measured basal salivary and plasma NO2(-) and NO3(-) in 13 adult volunteers.
• Assessed ex vivo salivary NO3(-) to NO2(-) reduction efficiency.
• Compared salivary reduction with plasma NO3(-) and NO2(-) changes after beetroot juice ingestion in 10 volunteers.

Main Results:

• No significant correlation was found between salivary and plasma NO2(-).
• No correlation existed between salivary NO3(-) and plasma NO2(-).
• Correlations were observed between salivary NO3(-) and plasma NO3(-), and between salivary NO2(-) and plasma NO3(-).
• Ex vivo salivary NO3(-) reduction did not correlate with plasma NO3(-) or NO2(-) increases post-beetroot juice.

Conclusions:

• Salivary nitrate (NO3(-)) and nitrite (NO2(-)) measurements are not reliable indicators of endothelial function or circulatory nitric oxide (NO) availability.
• The efficiency of saliva to reduce NO3(-) ex vivo does not predict the in vivo increase in plasma NO2(-) after dietary NO3(-) intake.