[Functional test with potassium chloride following long-term space mission].

To look into the potassiuretic function of kidneys in 11 cosmonauts on the second day post recovery after six-month MIR missions, functional testing with potassium chloride was performed. The following standard procedure was used before and after the missions: during morning hours fasting test-subjects consumed a 10% solution of potassium chloride in the amount of 0.55 ml/kg or 0.75 mmol of potassium per a kilogram of body mass with some additional liquid in the amount of 10 ml/kg of body mass. Later on, urine was collected for four hours. Administration of the potassium loading test after missions did not reveal any significant group-average changes in potassium excretion as compared with pre-flight levels; meanwhile, calcium excretion was increased. Reduced blood concentrations of potassium were determined in each of the cosmonauts immediately after landing. The main contributor to retaining of the renal potassiuretic function after prolonged missions appears to be the effective inflight physical countermeasures against the musculoskeletal deconditioning of the human body.