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Circadian variation in vascular tone and endothelial cell function in normal males
Khalid Elherik1, Faisel Khan, Margaret McLaren
1University Department of Medicine, Ninewells Hospital and Medical School, Dundee, Scotland DD1 9SY, UK.
Clinical Science (London, England : 1979)
|May 1, 2002
Summary
This study reveals that endothelial cell function, including nitric oxide (NO) and endothelin-1 (ET-1) levels, exhibits daily circadian rhythms in healthy males. These daily variations in vascular function may contribute to the timing of cardiovascular events, particularly in the morning.
Area of Science:
- Cardiovascular Physiology
- Chronobiology
- Endothelial Function
Background:
- Circadian rhythms influence the timing of acute cardiovascular events.
- Endothelial cell products like nitric oxide (NO) and endothelin-1 (ET-1) play critical roles in vascular tone.
- Understanding daily variations in endothelial function is key to explaining event timing.
Purpose of the Study:
- To investigate the circadian variation of endothelial cell products (NO and ET-1).
- To assess the daily rhythm of endothelium-dependent and -independent vasodilation.
- To explore the relationship between endothelial function and circadian rhythms in healthy males.
Main Methods:
- Measured plasma ET-1 and NO levels every 4 hours over 24 hours in nine healthy males.
- Assessed forearm skin vascular responses to acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent) using laser Doppler imaging every 4 hours.
- Utilized ANOVA for statistical analysis of circadian variations and correlation analysis for relationships between variables.
Main Results:
- Demonstrated significant circadian variation in acetylcholine-induced vasodilation, peaking in the afternoon and lowest in the morning.
- Observed significant circadian variation in sodium nitroprusside-induced vasodilation, with peaks in the afternoon and troughs in the early morning.
- Found significant circadian variation in ET-1 levels with morning and evening peaks, and a significant trend for NO levels with higher levels in the evening.
- Correlations indicated that ACh responses were significantly linked to both ET-1 and NO levels.
Conclusions:
- Endothelial cell activity exhibits a significant circadian variation, with reduced function observed in the morning.
- Circadian variations in endothelial function, influenced by ET-1 and NO, may contribute to the morning peak in acute cardiovascular events.
- These findings highlight the importance of daily rhythms in endothelial health and cardiovascular event occurrence.