Diurnal variation of aldosterone and plasma renin activity: timing relation to melatonin and cortisol and consistency after prolonged bed rest

• Published in: Journal of applied physiology (1985) 2004-04, Vol.96 (4), p.1406-1414
• Main Authors: Hurwitz, Shelley, Cohen, Richard J, Williams, Gordon H
• Format: Article
• Language: English
• Subjects: Adult; Aldosterone - blood; Bed Rest; Biological and medical sciences; Chronobiology; Circadian Rhythm; Fundamental and applied biological sciences. Psychology; Hormones; Humans; Hydrocortisone - blood; Male; Melatonin - blood; Middle Aged; Proteases; Renin - blood; Steroids; Time Factors; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00611.2003

1 Division of Endocrinology, Diabetes, and Hypertension and Clinical Research Center, Brigham and Women's Hospital and Sciences and Harvard Technology, Medical School, Boston 02115; and Massachusetts Institute of 2 Harvard-MIT Division of Health Technology, Cambridge, Massachusetts 02139 Submitted 13 June 2003 ; accepted in final form 26 November 2003 Exposure to prolonged bed rest is known to induce changes in the renin-angiotensin-aldosterone system (RAAS) by way of posture, sodium and potassium balance, and stress, which may have serious consequences for patients. We focused on the diurnal variation of the RAAS by investigating changes in the levels of plasma renin activity (PRA) and aldosterone; for comparison to markers of the intrinsic pacemaker and to stress, we measured melatonin and cortisol. PRA, aldosterone, melatonin, and cortisol were measured hourly in 10 normal subjects with standardized sleep patterns, posture, and diet at baseline and after 11 days of prolonged bed rest conducted under a light-dark cycle. Circadian characteristics of hormone secretion patterns were estimated by multiple harmonic regression with excellent goodness-of-fit measures. Variability in the melatonin and cortisol patterns across subjects was minimal. Even for pulsatile hormones, this technique successfully estimated the acrophase, which was the salient feature. Baseline hormone peak times started with melatonin near the middle of the sleep period, followed by PRA, then aldosterone, and then cortisol around wake time. Prolonged bed rest did not induce significant changes in any timing characteristic of the secretion patterns. Baseline and prolonged bed rest peak times for melatonin and cortisol and amplitude characteristics for all hormones were highly correlated, indicating consistency within individuals. These data provide strong evidence that prolonged bed rest of 11 days' duration does not disrupt either the timing characteristics of the RAAS or the intrinsic pacemaker. renin-angiotensin-aldosterone system; circadian rhythms; harmonic regression Address for reprint requests and other correspondence: S. Hurwitz, Center for Clinical Investigation, Brigham and Women's Hospital, 1620 Tremont St./BC-3, Boston, MA 02120-1613.