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Melatonin differentially affects vascular blood flow in humans.
Jonathan S Cook1, Charity L Sauder, Chester A Ray
1Pennsylvania State Heart and Vascular Institute, Department of Cellular and Molecular Physiology, General Clinical Research Center, Pennsylvania State University College of Medicine, H047, 500 Univ. Dr., Hershey, PA 17033-2390, USA.
American Journal of Physiology. Heart and Circulatory Physiology
|December 15, 2010
Summary
Melatonin supplementation differentially affects human blood flow, decreasing renal blood flow while increasing forearm blood flow. This suggests complex vascular effects, potentially mediated by sympathetic nervous system changes.
Area of Science:
- Physiology
- Pharmacology
- Cardiovascular Research
Background:
- Melatonin, a hormone produced by the pineal gland, regulates circadian rhythms.
- Animal studies indicate melatonin influences blood flow in various vascular beds via receptor activation.
- The specific effects of melatonin on human vascular beds remain incompletely understood.
Purpose of the Study:
- To investigate the impact of exogenous melatonin on human blood flow in renal, forearm, and cerebral circulations.
- To assess melatonin's effects on systemic hemodynamics, including arterial pressure and heart rate.
Main Methods:
- A randomized, placebo-controlled crossover study involving 10 healthy human subjects.
- Measurements included renal blood flow velocity, forearm blood flow, cerebral blood flow, arterial pressure, and heart rate.
- Vascular conductance was calculated to assess changes in blood flow regulation.
Main Results:
- Melatonin did not significantly alter heart rate or mean arterial pressure.
- Renal vascular conductance (RVC) decreased with melatonin administration, indicating renal vasoconstriction.
- Forearm blood flow and vascular conductance (FVC) increased with melatonin, suggesting vasodilation in this bed.
Conclusions:
- Exogenous melatonin exerts differential effects on human vascular beds, causing renal vasoconstriction and forearm vasodilation.
- The observed renal vasoconstriction may involve increased sympathetic outflow to the kidney.
- Melatonin's complex influence on human vasculature warrants further investigation.
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