Obstructive sleep apnea treatment: peripheral and central effects on plasma renin activity and aldosterone

To assess the effect of obstructive sleep apnea treatment on plasma renin activity (PRA) and plasma aldosterone seven male patients were studied under two conditions: untreated and treated with nasal continuous positive airways pressure (CPAP). PRA and plasma aldosterone were measured at 10-min intervals for both nights. CPAP treatment diminished the urinary and Na+ excretion, whereas plasma volume increased. The mean levels of PRA and aldosterone were significantly enhanced by the treatment, increasing respectively from 1.5 +/- 0.3 to 3.0 +/- 0.7 ngAI ml-1.hr-1 (p less than 0.05) and from 8.0 +/- 1.0 to 12.0 +/- 1.7 ng.100 ml-1 (p less than 0.05). PRA curves reflected the overall sleep structure as similarly described in normal subjects. The apnea-induced sleep disturbance led to flat PRA profiles and the restoration of a normal sleep pattern by treatment restored the PRA oscillations related to the sleep cycles and consequently restored aldosterone oscillations. The mean amplitude of these oscillations increased respectively from 1.0 +/- 0.1 to 1.8 +/- 0.4 ngAI ml-1.hr-1 and from 5.4 +/- 1.2 to 10.9 +/- 1.9 ng.100 ml-1. These results suggest that CPAP treatment modifies the nocturnal patterns of PRA and aldosterone by increasing their mean levels and their oscillation amplitude. This indicates increased secretion, which contributes to the normalization of urine and Na output.