ROLE OF THE RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM IN THE PATHOGENESIS OF ARTERIAL-HYPERTENSION IN OBSTRUCTIVE SLEEP-APNEA (OSA)

The improvement of arterial hypertension during treatment of sleep apnea with nasal continuous positive air pressure (nCPAP) ventilation may be an indicator for a pathophysiological linkage. We studied the influence of sleep apnea on the renin-angiotensin-aldosterone-system (RAAS) in 6 patients in a night before and during nCPAP therapy. Although no differences were observed before sleep onset, renin secretion was significantly higher between 2:00 and 6:00 during treatment. Angiotensin 11 and aldosterone showed a concordant reaction. The typical sleep-associated increase of renin secretion was found only in the night on nCPAP. Since the reaction of the RAAS was contrary to the well-known decrease of blood pressure during treatment, we concluded that the RAAS may not be involved in the development of nighttime hypertension in sleep apnea. In accordance with recently demonstrated changes in atrial natriuretic peptide (ANP) secretion the RAAS is a further indicator for a hypervolemic reaction pattern during apnea which is corrected by treatment. Therefore, nycturia before treatment can be explained by the demonstrated changes in volume-regulating hormones. Besides stimulated ANP secretion activation of cardiopulmonary stretch receptors may cause the suppression of renin secretion. The presented data indicate complex disturbances in volume homeostasis which may play a central role in the pathogenesis of cardiovascular sequelae in sleep apnea.