Vasopressin Not Aldosterone is associated with Changes in Body Mass and Urine Volume during a Controlled 4 d Fluid Intake Intervention

Abstract

Arginine vasopressin (AVP) and aldosterone (ALDO) act on renal nephrons to conserve water and sodium in response to decreased total body water, across a wide range of human 24‐h fluid intakes (FI). It is unknown if resting values of AVP or ALDO differ between habitual high FI (HIGH) and low FI (LOW) women during daily activities, and how these groups respond to FI modification. Therefore, the diet records of 120 women were analyzed to identify 14 HIGH (3.34 ± 0.56 L/d) and 14 LOW (1.62 ± 0.48 L/d). Next, the FI of HIGH was reduced (2.00 ± 0.21 L/d) and LOW was increased (3.50 ± 0.13 L/d) over 4d via water prescription. Urinary and blood variables were measured each morning. No main effects of treatment were observed for body mass or ALDO. However, significant interactions, time X treatment, were observed for AVP (F[2, 22] = 40.16, p<.001), and urine volume (F[2, 26]=46.15, p<.001). Post‐hoc tests showed a significant difference in AVP; (F[1, 11] = 83.32, p< .001) from baseline (3.93 ± 1.34, 8.99 ± 2.69 pg/mL) to treatment (8.24 ± 3.22, 4.82±1.08 pg/mL) and in urine volume F(1, 13) = 61.95, p<.001 from baseline (1.90 ± 0.56, 0.79±0.26 L/d) to treatment (1.24 ± 0.22, 2.23 ± 0.44 L/d) between HIGH and LOW respectively. These results demonstrate that changes in AVP, not ALDO, (a) provide the primary defense of total body water, and (b) distinguish small changes (1.1 – 1.5 L/d) in daily FI. Supported by Danone Research, France.