Red blood of cosmonauts during missions aboard the international space station (ISS)

Morphological and biochemical investigations of red blood in cosmonauts on board the International Space Station (ISS) (from the 6th to the 12th expeditions) in the space experiment program “Hematology” were carried out 30 days before the space mission (SM), at the initial (days 6–10) and final (days 160–190) stages of SM, and after the SM (immediately after SM (day 0) and on the 7th and 15th days of the adaptation period to earth conditions). A reduction of the concentration of hemoglobin after a prolonged influence of SM factors has been found, which is probably related not only to the intensity of erythropoiesis but also with the possible early removal of a part of low-quality (probably, old) erythrocytes from the bloodstream, which is confirmed by the results on the metabolism of red blood cells and the state of the cell membrane. Stimulation of erythropoiesis (increase in erythropoietin, decreased level of iron in blood, removal of low-quality and old erythrocytes) in the period of readaptation to conditions on earth is aimed at maintenance of the optimal level of red blood cells required for increased oxygen demand in tissues under the conditions of earth gravitation and enhancement of muscular load.