Fluid-electrolyte metabolism and renal function of white rats in experiments aboard Cosmos biosatellites

Rat experiments on the Cosmos biosatellites demonstrated that the percentage of renal excretion of consumed water after flight was lower than after synchronous experiment. This can be attributed not only to water retention but also to a different level of extrarenal losses postflight. Weightless rats showed increased sodium excretion after water load tests and increased potassium excretion after potassium load tests. The sodium, potassium, and calcium balance was positive after weightlessness. Analysis of the electrolyte composition of different kidney zones revealed a decreased potassium content in the medulla, which is considered to be one of the causes of changed renal iono- and osmoregulatory function in weightlessness. The normalizing effect of artificial gravity on the natri- and kaliuretic renal function was demonstrated.