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Sympathetic activation and nitric oxide function in early hypertension.
Alfredo Gamboa1, Luis E Okamoto, André Diedrich
1Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University, Nashville, Tennessee, USA. alfredo.gamboa@vanderbilt.edu
American Journal of Physiology. Heart and Circulatory Physiology
|January 31, 2012
Summary
Nitric oxide (NO) tonically restrains blood pressure. This study found no evidence that NO
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
- Nitric Oxide Biology
Background:
- Impaired nitric oxide (NO) function is implicated in hypertension development.
- The precise role of NO in vascular tone versus sympathetic activity modulation remains unclear.
Purpose of the Study:
- To investigate if tonic blood pressure regulation by NO is impaired early in hypertension.
- To differentiate NO's direct effects on vascular tone from its indirect modulation of sympathetic activity.
Main Methods:
- Administered NO synthase inhibitor (L-NMMA) during autonomic blockade (trimethaphan) in normotensive, prehypertensive, and hypertensive subjects.
- Monitored blood pressure response to L-NMMA to assess NO's modulation of vascular tone.
- Included smokers as controls for impaired NO function.
Main Results:
- L-NMMA increased systolic blood pressure similarly in normal, prehypertensive, and hypertensive individuals (approx. 30-32 mmHg).
- Smokers showed a blunted response to L-NMMA, confirming impaired NO function.
- Trimethaphan normalized blood pressure in hypertensives, indicating increased sympathetic tone.
Conclusions:
- Nitric oxide (NO) tonically restrains blood pressure by approximately 30 mmHg.
- No evidence suggests impaired NO modulation of vascular tone contributes to early hypertension.
- NO's role in hypertension may involve modulation of the autonomic nervous system, not directly vascular tone.
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