Nitric Oxide Metabolites
Overview
Nitric oxide metabolites measure stable breakdown products of nitric oxide (NO), primarily nitrite (NO₂⁻) and nitrate (NO₃⁻), which reflect systemic NO production from endothelial, neuronal, and immune cells. Nitric oxide serves as a key vasodilator, neurotransmitter, and antimicrobial defense molecule; its metabolites indicate endothelial function, inflammation, and oxidative stress balance. Elevated levels suggest inflammation, infection, or endothelial dysfunction, while low levels may indicate reduced NO bioavailability in cardiovascular disease. These measurements remain primarily research tools rather than routine clinical tests due to variability and lack of standardized reference ranges.
Clinical Use Cases
- Research assessment of endothelial dysfunction in cardiovascular disease.
- Evaluating inflammation and immune activation in sepsis or autoimmune disorders.
- Investigating pulmonary hypertension and nitric oxide inhalation therapy response.
- Studying exercise physiology and vascular health.
Specimen Types
- Plasma.
- Serum.
- Urine (24-hour collection).
- Saliva.
Measurement Methods
- Griess reaction (colorimetric nitrite/nitrate assay).
- High-performance liquid chromatography (HPLC).
- Chemiluminescence gas analysis.
- Mass spectrometry (LC-MS/MS).
Test Preparation and Influencing Factors
- Avoid nitrate-rich foods (beets, leafy greens) and mouthwash for 24-48 hours.
- Recent meals, exercise, or tobacco use transiently elevate levels.
- Renal function affects plasma clearance; dietary nitrate confounds urine measurements.
- Sample processing critical: avoid room temperature storage to prevent conversion.
Synonyms
- NO₂/NO₃.
- NOx (total nitrite/nitrate).
- Serum nitrate/nitrite.