title: Diurnal variation of flow-mediated vasodilation in healthy premenopausal women.
abstract: 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.
authors.affiliation: Department of Clinical Physiology, Göteborg University, Sahlgrenska University Hospital, SE 413 45 Göteborg, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Ringqvist
authors.forename: K
authors.initials: K
authors.lastname: Caidahl
authors.forename: A S
authors.initials: AS
authors.lastname: Petersson
authors.forename: A
authors.initials: A
authors.lastname: Wennmalm
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001916:Brachial Artery / Q000502:physiology; D002395:Catecholamines / Q000097:blood; D002940:Circadian Rhythm / Q000502:physiology*; D006152:Cyclic GMP / Q000378:metabolism; D004730:Endothelium, Vascular / Q000378:metabolism; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008055:Lipids / Q000097:blood; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D005996:Nitroglycerin / Q000008:administration & dosage; D017697:Premenopause / Q000502:physiology*; D012016:Reference Values; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000008:administration & dosage
chemical_list: D002395:Catecholamines; D008055:Lipids; D009566:Nitrates; D014665:Vasodilator Agents; D009569:Nitric Oxide; D005996:Nitroglycerin; D006152:Cyclic GMP; D006854:Hydrocortisone