Figure 3

Circadian predictions of the vasopressin release and related physiological parameters generated by a simulation of 20 consecutive days. In the current rat model, the hydromineral status of the body fluid compartments is characterized by the ECF [Na⁺] (A), the ICF volume (C) and the ECF volume (D). The Inputs/outputs are the cumulative water intake (F) and cumulative urine (E), respectively and the systemic AVP concentration is the controller of the homeostasis (B). In each panel, the value of the parameter is calculated every minute and the solid black line is the mean of the parameter. The vertical bars are the standard deviation. The gray area illustrates the sleeping period of the rat (day) and the white area, the waking period (night). The prediction of the dynamic of the parameters highlights three distinct phases in the circadian fluctuation of the hydromineral balance: (1) the sleeping phase characterized by a progressive rise in ECF [Na⁺] and AVP, (2) the restoration phase (onset at the dotted line 1) covers the recovery of AVP from its peak to basal level and (3) the maintenance phase (onset at the dotted line 2) is characterized by the low variability of AVP level and a restored ECF [Na⁺] and volume.