[Biosynthesis of rat hemoglobin fractions under normal and increased erythropoiesis].

Studies of erythroid elements of hematopoietic organs and peripheric blood and bone marrow cell populations fractionated by precipitation in an albumin density gradient and synchronized by actinomycin D revealed that the rate of synthesis of individual haemoglobin fractions in the course of erythropoiesis is changed. The proliferating cells are characterized by a predominant accumulation of haemoglobin in fractions with beta c-and in the maturing cells--with beta b-chains. The radioactivity in the whole population of hematopoietic organs under phenylhydrazine anemia is mainly increased in the beta c-chains, whereas under the effects of erythropoietic factors (erythropoietin, animal sera)--that of beta b-chains is increased. In early erythroblasts the erythropoietic factors activate the formation of beta c-chains and in late ones--that of beta b-chains. Similar time dependence was observed in case of synthesis and activation of alpha b- and alpha a-chains. The specific cell responses in the erythroid series of bone marrow, spleen and blood to the effects of erythropoietic factors and anemia were established. The molecular mechanisms involved in the switch-over of the synthesis of various haemoglobin chains are discussed.