Effects of Sodium Depletion and Orthostasis on Plasma and Urinary Vasopressin in Normal Subjects.

Abstract

We investigated the effects of sodium depletion and orthostasis on the plasma concentration and urinary excretion of vasopressin (AVP) in eight normal female subjects. After 4 days on a sodium controlled diet (130 mEq/ day), the subjects were placed on a low sodium diet (30 mEq/day) for 3 days and 120mg of furosemide was administered orally on the first day of the low sodium regimen.Sodium depletion in the present study reduced body weight by 1.6 kg and increased hematocrit by 3.5%.A significant (p<0.05) increase in plasma AVP and a significant (p<0.05) decrease in 24-h urinary excretion of AVP were observed during sodium depletion.One-hour ambulation significantly increased plasma AVP in both control and sodium depleted phases (p<0.01).The percent change in plasma AVP tended to correlate with that in mean blood pressure in the control phase (r= 0.69, 0.05<p<0.1), and significantly correlated in the sodium depleted phase (r=0.86, p<0.01).The present results suggest that AVP may play an important role in the maintenance of blood pressure during orthostasis in the sodium depleted state.

Comparison between men and women of volume regulating hormones and aquaporin-2 excretion following graded central hypovolemia

“…It has been shown that supine to erect posture change as well as ambulation increase AVP levels (Cignarelli et al, 1986, Tsuchihashi et al 1989). Furthermore, it has been shown that plasma AVP levels adjust rapidly within approximately 10 minutes upon posture changes (Pump et al, 1999).…”