Basal nitric oxide synthesis in essential hypertension

Area of Science:

• Cardiovascular Research
• Endocrinology
• Metabolic Studies

Background:

• Essential hypertension is linked to altered nitric oxide (NO) synthesis in vascular endothelium.
• Direct measurement of NO production in hypertension is challenging.
• Nitrate, the end product of NO oxidation, serves as a biomarker for NO synthesis.

Purpose of the Study:

• To directly estimate nitric oxide (NO) production in patients with untreated essential hypertension.
• To measure inorganic nitrate synthesis as an indicator of NO production.
• To investigate the relationship between blood pressure and NO synthesis.

Main Methods:

• Two studies were conducted involving patients with hypertension and healthy controls.
• Study 1: Dietary nitrate intake, urinary/plasma nitrate measurement, and 24-hour ambulatory blood pressure monitoring.
• Study 2: Intravenous L[15N]2 arginine administration, 24-hour ambulatory blood pressure monitoring, and 36-hour urine collection for 15N-nitrate measurement.

Main Results:

• Hypertensive patients showed significantly lower 24-hour urinary nitrate excretion compared to controls in Study 1 (p < 0.001).
• A significant inverse correlation was observed between daytime blood pressure and nitrate excretion (p = 0.007).
• Hypertensive patients exhibited lower 36-hour urinary 15N-nitrate excretion (p < 0.001) and an inverse correlation with blood pressure (p = 0.002) in Study 2.

Conclusions:

• Whole-body nitric oxide (NO) production appears diminished in patients with essential hypertension under basal conditions.
• The precise origin of the measured NO is undetermined.
• It remains unclear whether the impaired NO synthesis is a primary cause or a consequence of elevated blood pressure.