[Molecular-genetic mechanisms of regulation of synthesis of individual types of rat hemoglobin].

The effects of actinomycin D and erythropoietically active serum (EAS) on the synthesis of beta-like chains of haemoglobin in the erythroid cells of rat bone marrow in vivo and in vitro were studied. It was shown that in the whole population of erythroid elements of bone marrow actinomycin D sharply decreases the synthesis of beta c-chains, whereas in early erythroblasts it predominantly inhibits the synthesis of beta b-chains. In the whole population of rat bone marrow cells EAS activates the predominant formation of beta b-chains. Under a combined administration of actinomycin D and EAS the stimulating effect of the latter manifests itself not earlier than 24 hrs after the antibiotic injection. The effect of actinomycin D is removed after injection of EAS to the animals, especially during the first 12 hrs. In the culture of anaemic animals bone marrow in the presence of EAS the highest amount of the label is detected in the beta c-chains, whereas in the erythroid elements treated with the erythropoietic factors in vivo--in the beta b-chains. Actinomycin D has no pronounced effect on the rate of beta-like chain formation in a short-time culture of bone marrow. The molecular mechanisms which control the switch-off of the predominant synthesis in different polypeptide types are discussed.