Effect of water immersion on renin-aldosterone and renal sodium handling in normal man.

Cardiovascular Adjustments to Gravitational Stress

“…The role of atrial distension has been disputed (115). Epstein et al (87,89,90) have clearly documented inhibition of the renin-aldosterone system and a sal uresis during immersion experiments. Their data also indicate that it is unlikely that osmoreceptors or changes in renal hemodynamics have a major role.…”

“…Angiotensin II release can stimulate the central nervous system and augment sympathetic vaso-and venoconstriction, but the direct and indirect hemodynamic effects are physiologically important only in the sodium-depleted state (97,298). Activating the cardiopulmonary mechanoreceptors by distension inhibits both antidiuretic hormone (ADH) and renin-aldosterone and produces a diuresis (87,89,90,107).…”

“…The fluidrelated weight loss occurs within 3-4 days during bed rest (127,340) (90). The average total weight loss during flights of 28-84 days in the nine Skylab crew members was 3 kg, corresponding to 4% of total body weight (335,336).…”

Impaired Atrial Receptor Responses in Dogs with Heart Failure Due to Tricuspid Insufficiency and Pulmonary Artery Stenosis

“…Such structures could be affected by the changes occurring during heart failure. This effect is important because, in their studies of the effects of water immersion on renin-aldosterone levels and renal sodium handling in normal man, Epstein and Saruta (26) suggested that these particular cardiac receptors could be involved. In related work Thames et al (27) and Goetz et al (28) reached similar conclusions.…”

Cardiovascular and renal effects of head-out water immersion in man: application of the model in the assessment of volume homeostasis.

“…When the depth of immersion was varied, it was demonstrated that water immersion to the waist did not induce a natriuresis in either sodium-depleted 33 or sodium-replete subjects. 20 …”