Water and electrolyte studies during long-term missions onboard the space stations SALYUT and MIR

Abstract

This contribution summarizes the results of investigations of water-electrolyte metabolism and its hormonal regulation conducted in cosmonauts who performed long-term space flights (from 18 to 366 days) aboard the space stations Salyut and Mir and compares them with the results obtained during various NASA flights. The role of the kidneys in ion metabolism regulation was assessed by various water-salt load tests before and after flights. In addition, the results of a year-long space flight and of medical experiments performed during the 237- and 241-day missions by the physicians and cosmonaut-researchers Atkov and Polyakov are reviewed in detail. In spite of interindividual variations, metabolic, and endocrine studies during prolonged space flights showed a reduction in body mass, usually with a reduction in body water and electrolytes and considerable changes in blood hormone concentrations and urinary hormone excretion. These changes reflect the processes of extended adaptation to a new environment. It is likely that shifts in electrolyte metabolism in weightlessness are primarily due to metabolic changes that diminish the tissue ability for ion retention and to concomitant changes in the endocrine status. The postflight examinations revealed changes in fluid-electrolyte metabolism and in the function of the kidneys which indicated a hypohydration status and a stimulation of hormonal systems responsible for fluid-electrolyte homeostasis in order to readapt to the normal gravitation. Postflight decline in osmotic concentration of urine in cosmonauts was accompanied by an altered response to antidiuretic hormone and was probably caused by changes in the functional state of the kidneys. We conclude that detailed knowledge of the alterations in water-electrolyte metabolism and its hormonal regulation on different stages of space flight are important prerequisites for the development of countermeasures to space deconditioning and thus for increased human efficiency in space. In addition, these data contribute to an increase in our general knowledge on the regulation of kidney function.

Does resistance exercise prevent body fluid changes after a 90-day bed rest?

“…1996) and (2) a loss of plasma volume (PV) triggered by the activation of the Henry-Gauer reflex and disturbed secretion of PV-regulating hormones (Fortney et al 1996;Gharib et al 1992;Maillet et al 1994Maillet et al , 2000. Later on in the mission, TBW decreases further, accompanied by the loss of lean tissue (Blanc et al 1998;Lane and Feeback 2002;Parsons et al 2000) and a diminished sensation of thirst (Grigoriev et al 1994;Leach-Huntoon et al 1998;Leach et al 1996). To prevent these perturbations in fluid homeostasis, several countermeasures have been tested during actual and simulated weightlessness.…”

Low Urinary Albumin Excretion in Astronauts during Space Missions

“…They include an increased urinary calcium excretion, the tendency to sodium retention, and an increased glomerular filtration during the first days of missions [3, 4, 5, 6, 7]. The risk of proteinuria, hence of renal damage, during space mission was also hypothesized [8]but research data are not available. Urinary albumin excretion is extremely low in healthy individuals: it is considered a sensitive index of glomerular protein handling and increases also for early renal damage [9].…”

The Risk of Renal Stone Formation during and after Long Duration Space Flight

“…However, human exposure to the weightless environment produces many changes, both acute and chronic, to all physiologic systems of the human body [1, 2]. Changes to the cardiovascular, skeletal, muscular, and fluid-regulating systems are well-documented both during flight and upon return to Earth [3, 4, 5]. …”