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The paper presents the results of studying fluid-electrolyte metabolism and the renal function in A. A. Gubarev and G. M. Grechko after their 30-cay orbital flight. On the R + O day renal excretion of fluid, sodium, potassium and osmotically active subtances decreased. Renal excretion of calcium and magnesium postflight was higher than preflight. Similar, although better pronounced, changes were seen during provocative tests with a water load. One of the factors causing changes in the renal transport of electrolytes postflight could have been an alteration in the ionic composition of the serum, especially a decrease in the potassium concentration and an increase in the calcium and magnesium content. Disorders in the relationship between the function of osmo- and ion regulation systems and dissociation in the renal excretion of individual ions after the 30-day flight that were distinct during tests with a water load seem to be associated with metabolic changes during and after flight rather than with hemodynamic changes.

Ten cosmonauts who performed 30- to 175-day space flights on board Salyut-4 and Salyut-6, and 50 test subjects exposed to head-down tilt (-4 degrees) for 182 days were examined. In actual and stimulated weightlessness renal excretion of calcium and potassium increased, reaching maximum during the 4-6th weeks. Before and after flight the test subjects were exposed to loading salt tests. Renal excretion of calcium and potassium in response to the loading tests with their salts postflight was much higher than preflight. During the potassium chloride load the aldosterone content in blood correlated with potassium excretion, and during the calcium lactate load an increase in calcium excretion was paralleled by a decrease in the parathormone content in blood. It is most likely that the negative balance of ions in weightlessness is associated with the reduced capacity of tissues to retain electrolytes due to the decreased ion pool. It was shown that electrolyte balance can be beneficially influenced by exercises.

Intake of fluid, water-salt solutions, water and sodium chloride resulted in hyperhydration, the level and duration of which varied with respect to the pattern and composition of the ingredients consumed. As applied to real space flights, fractional consumption of water and sodium chloride proved most promising. This regimen yielded a distinct and prolonged hyperhydration and incrased orthostatic and LBNP tolerance of the test subjects.

The paper presents the results of studying the fluid-electrolyte metabolism in P. I. Klimuk and V. I. Sevastyanov before and after their 63-day flight aboard the orbital station Salyut-4. Postflight weight losses in P.I. Klimuk and V.I. Sevastyanov were 5.6 and 3.5%, respectively, the losses being attributed to body dehydration. Postflight both cosmonauts showed a trend for an increased renal excretion of potassium, magnesium, and calcium as compared with their food intake. Those were more expressed on the day after the water load application. Possible causes of the changes and the pattern of recovery of fluid-electrolyte metabolism after a prolonged space flight are discussed.