| Blood Press 2003;12(1):19-24 |
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| Impaired nocturnal melatonin secretion in non-dipper hypertensive
patients |
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| Jonas M, Garfinkel D, Zisapel N, Laudon M, Grossman E. |
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| Department of Internal Medicine D. The Chaim Sheba Medical Center,
Tel-Hashomer, Israel. |
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BACKGROUND: Melatonin plays a role in the biologic regulation of
circadian rhythms, including sleep. Melatonin has also been shown to
modulate vascular smooth muscle tone and to induce hemodynamic effects
in humans. OBJECTIVE: To evaluate whether melatonin plays a role in
the circadian rhythm of blood pressure in hypertensive patients. METHODS:
Sixteen elderly patients with essential hypertension were evaluated.
Patients were defined as either dippers (DIP, n = 8) or non-dippers
(NDIP, n = 8) according to the nocturnal change in the mean arterial
pressure (MAP). 6-Sulfatoxymelatonin (6-SMT), the main melatonin metabolite,
was determined by enzyme-linked immunosorbent assay (ELISA) in two
separate urine collections, one in the daytime and one during the night.
RESULTS: Both groups of DIP and NDIP hypertensives were comparable
in regard to age and sex. During the night, the mean arterial pressure
decreased by 10.3 +/- 2.2% in the DIP and increased by 7.5 +/- 1.7%
in the NDIP group (p < 0.01). Daily 6-SMT was comparable in DIP
(3.28 +/- 0.87 microg/12 h) and NDIP (2.31 +/- 0.68 microg/12 h) (p
= 0.39). However, while the DIP presented the physiological nocturnal
increase in urinary 6-SMT (mean 8.19 +/- 1.68 microg/ 12 h), this surge
of melatonin production was missing in NDIP in whom nocturnal urinary
6-SMT concentrations were not significantly different from daily levels
(mean 2.56 +/- 0.79 microg/12 h). The nocturnal change in urinary 6-SMT
excretion was positively correlated to the nocturnal change in MAP
(R = 0.54; p = 0.031). CONCLUSIONS: NDIP hypertensive patients differ
from DIP hypertensives by having an impaired nocturnal melatonin secretion.
Thus, melatonin may play a role in the circadian rhythm of blood pressure
in hypertensive patients.
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