[Effect of space flight factors on the hormonal regulation of water-salt metabolism].

This paper presents the results of examinations of 19 test subjects exposed to head-down tilting at -8 and -15 degrees and of 14 test subjects kept in water immersion for 24 hours. During the first hours of exposure the renal excretion of water and monovalent ions increased. Renin and aldosterone measurements showed that changes in the sodium and potassium excretion were produced by a lower activity of the renin-angiotensin-aldosterone system in the first 1.5 hour of hypokinesia. During immersion the renal excretion of calcium and magnesium also grew, especially in the evening and at night. The PTH production and calcium concentration in blood increased, thus augmenting the nephron load. The diurnal rhythms of the renal excretion of potassium, calcium and magnesium remained unchanged and those of water, osmotically active substances and sodium varied. The data obtained indicate significant changes in water-salt metabolism and its regulation within the first hours of head-down tilt and water immersion.