Renal nitrate clearance in chronic kidney disease

Area of Science:

• Cardiovascular Physiology
• Renal Physiology
• Nitric Oxide Metabolism

Background:

• Nitric oxide (NO) is metabolized to nitrite and nitrate in the body.
• Nitrate can be recycled to NO via the entero-salivary pathway, preserving NO activity.
• The renal excretion pathway for nitrate and the impact of declining kidney function are not fully understood.

Purpose of the Study:

• To investigate the relationship between renal function and nitrate clearance.
• To determine how declining kidney function affects plasma nitrate concentration and urinary nitrate excretion.

Main Methods:

• Forty-five subjects with varying renal function (eGFR 9-89 ml/min/1.73 m²) participated.
• Subjects followed a low-nitrate diet for 24 hours.
• Plasma nitrate concentration and 24-hour urinary nitrate excretion were measured using spectrophotometry to calculate renal nitrate clearance.

Main Results:

• A significant positive correlation was found between urinary nitrate clearance and estimated glomerular filtration rate (eGFR) (R=0.7665, p<0.0001).
• Plasma nitrate concentration showed a significant negative correlation with eGFR (R=-0.37, p=0.012).
• Plasma nitrate concentration was positively correlated with serum creatinine (R=0.39, p=0.008).

Conclusions:

• Renal nitrate clearance is strongly associated with renal function.
• Plasma nitrate levels rise as renal function declines.
• Urinary nitrate excretion may not be a reliable indicator of endogenous NO synthesis in individuals with impaired kidney function.