RESUMEN
Fluid-electrolyte metabolism and renal function of the crewmembers of the 185-day space flight were examined. Various changes in fluid-electrolyte metabolism and its regulation were seen in the Commander and Flight-Engineer. As most other crewmembers who performed similar flights, Cr showed fluid and sodium retention, whereas FE displayed higher than preflight sodium excretion in the urine. These differences were associated with individual variations of regional hemodynamics which modified the renin-angiotensin-aldosterone system in a different manner. Postflight both crewmembers showed a higher excretion of bivalent ions. The higher excretion of calcium was accompanied by a lower concentration of total and ionized calcium in the serum as well as by a lower concentration of PTH and calcitonin. The loading KC1 test made it possible to assess variations in potassium metabolism that occurred during flight. They included the inability of tissues to retain potassium due to atrophic processes which developed in the weightless state and due to the unloading of the musculoskeletal system.