Diurnal variation of flow-mediated vasodilation in healthy premenopausal women

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 279; no. 6; pp. H2720 - H2725
• Main Authors: Ringqvist, Asa, Caidahl, Kenneth, Petersson, Ann-Sofi, Wennmalm, Ake
• Format: Journal Article
• Language: English
• Published: United States 01.12.2000
• Subjects: Adult; Blood Pressure - physiology; Brachial Artery - physiology; Catecholamines - blood; Circadian Rhythm - physiology; Cyclic GMP - metabolism; Endothelium, Vascular - metabolism; Female; Heart Rate - physiology; Humans; Hydrocortisone - blood; Lipids - blood; Nitrates - metabolism; Nitric Oxide - metabolism; Nitroglycerin - administration & dosage; Premenopause - physiology; Reference Values; Vasodilation - drug effects; Vasodilation - physiology; Vasodilator Agents - administration & dosage
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2000.279.6.h2720

Department of Clinical Physiology, Göteborg University, Sahlgrenska University Hospital, SE 413 45 Göteborg, Sweden The present study was designed to test the hypothesis of a diurnal variation of endothelial function. Sixteen healthy, nonsmoking women were studied, each on four occasions during one 24-h period (2:00 PM, 8:00 PM, 2:00 AM, and 8:00 AM). Endothelial function was assessed by ultrasound determinations of flow-mediated vasodilation (FMD%) in the brachial artery. FMD% was contrasted with endothelium-independent vasodilation, i.e., nitroglycerine-induced vasodilation (NTG%). Additionally, plasma concentrations and urinary excretion of nitrate and cGMP were analyzed. FMD% and NTG% displayed diurnal, albeit not parallel, patterns of variation. Whereas FMD% gradually increased from 2:00 PM and peaked at 2:00 AM (means ± SE: 3.1 ± 0.4, 4.4   ± 0.4, 5.1 ± 0.9, and 3.9 ± 0.8%), the NTG% demonstrated a nadir at 2:00 AM. Plasma levels and urinary excretion of nitrate and cGMP did not display diurnal variation and no clear association with the variations seen in FMD% and NTG%. This study demonstrates a diurnal variation in both endothelium-dependent and -independent vasodilation in the brachial artery of healthy women. The background and possible implication of such a variation require further studies. nitric oxide; nitrate; guanosine 3',5'-cyclic monophosphate; endothelium; catecholamines