Time‐courses in renin and blood pressure during sleep in humans

We previously described a strong concordance between nocturnal oscillations in plasma renin activity (PRA) and the rapid eye movement (REM) and non‐REM (NREM) sleep cycles, but the mechanisms inducing PRA oscillations remain to be identified. This study was designed to examine whether they are linked to sleep stage‐related changes in arterial blood pressure (ABP). Analysis of sleep electroencephalographic (EEG) activity in the delta frequency band, intra‐arterial pressure, and PRA measured every 10 min was performed in eight healthy subjects. Simultaneously, the ratio of low frequency power to low frequency power + high frequency power [LF/(LF + HF)] was calculated using spectral analysis of R–R intervals. The cascade of physiological events that led to increased renin release during NREM sleep could be characterized. First, the LF/(LF + HF) ratio significantly (P < 10−4) decreased, indicating a reduction in sympathetic tone, concomitantly to a significant (P < 10−3) decrease in mean arterial pressure (MAP). Delta wave activity increased (P < 10−4) 10–20 min later and was associated with a lag of 0–10 min with a significant rise in PRA (P < 10−4). Rapid eye movement sleep was characterized by a significant increase (P < 10−4) in the LF/(LF + HF) ratio and a decrease (P < 10−4) in delta wave activity and PRA, whereas MAP levels were highly variable. Overnight cross‐correlation analysis revealed that MAP was inversely correlated with delta wave activity and with PRA (P < 0.01 in all subjects but one). These results suggest that pressure‐dependent mechanisms elicit the nocturnal PRA oscillations rather than common central processes controlling both the generation of slow waves and the release of renin from the kidney.