[Hemopoietic status of rats exposed to weightlessness]

This paper summarizes experimental data on the erythropoiesis of rats flown on Cosmos biosatellites for 18-22 days. The histogenesis of the hemopoietic tissue is investigated at the level of stem cells, dividing-maturing pool and mature blood cells (erythrocytes). In weightlessness inhibition of the erythropoiesis in various skeletal sites occurs. Flight data are compared with hemopoietic findings in hypokinetic rats. Possible mechanisms underlying red blood disorders in humans during space flight are discussed.