Circadian rhythm of the renin-angiotensin-aldosterone system: a summary of our research studies.

The renin-angiotensin-aldosterone system (RAAS) is characterized by a circadian rhythm (CR) whose acrophase is detectable early in the morning. The prorenin and angiotensin converting enzyme (ACE) show a CR as well. However, while the prorenin is in phase with the RAAS the ACE shows its circadian acrophase in the afternoon suggesting a negative feed-back. The RAAS CR is influenced by many factors. Its mesor is modified by sodium intake. The physical activity and rest affect both the mesor and acrophase. The variations in mesor amplitude and acrophase in aged subjects are conditioned by sex and physical activity. Moreover, the RAAS CR seems to be influenced by the race. In addition, it is abolished by the beta-adrenergic blockade, suggesting the existence of an adrenergic clock. Interestingly, the RAAS CR seems not to be a pacemaker for the blood pressure CR, whose acrophase is early in the afternoon. The RAAS CR is not substantially modified has in essential hypertension. However, the CR of plasma renin activity is disappeared in the low-renin essential hypertension, while the CR of plasma aldosterone is detectable. On the contrary, the aldosterone CR is not detectable in ascitic liver cirrhosis; but, it is restored when the ascites is removed by peritoneal-jugular shunt. No significant variation of the RAAS CR seems to occur in obesity and Cushing's syndrome. The RAAS CR has disappeared in Conn's disease as well as in Bartter's syndrome and Liddle's syndrome. The administration of indomethacine in Bartter's syndrome and of triamterene in Liddle's syndrome is able to restore the RAAS CR. Finally, the RAAS CR is not detectable in the heart or kidney transplanted patients; such a phenomenon could be attributed to cyclosporine and corticosteroids administration and to the denervation of the transplanted organs.