Studies on the regulation of erythropoiesis on fetal calf liver cells

Canas, Patricio Eudardo.

Biology, General.

The mechanism of action of erythropoietin (EPO) and the effects of different cyclic nucleotides on hemoglobin synthesis have been studied using a serum-free system of fetal calf liver cells. dbcAMP, dbcGMP and cCMP stimulated hemoglobin synthesis at different concentrations, and their effects were quite different depending on the type of hemoglobin being synthesized. The analysis of (alpha) and (gamma) chains by high pressure liquid chromatography (HPLC) indicated that both the (alpha) and (gamma) globin chains are stimulated by the three cyclic nucleotides. Furthermore, Step III sheep plasma EPO stimulated the synthesis of cGMP in fetal calf liver cells. On the other hand, only cGMP stimulated the nuclear RNA polymerases measured at low ionic strength in the presence of methyl-isobutyl-xanthine (MIX), an inhibitor of phosphodiesterase. These results indicate that cGMP could be one of the second messengers of EPO on the stimulation of RNA synthesis and probably hemoglobin synthesis.

EPO also stimulated the RNA polymerase activities of fetal calf liver cells after one hour of incubation in vitro. This stimulation seems to be mediated by some factors present in the cytoplasm of treated cells, because nuclei incubated with this cytoplasmic preparation had a higher RNA polymerase activity than those incubated with cytoplasmic preparations of control cell cultures. The nature of these cytoplasmic factors are heterogenous, because the type of RNA polymerase stimulated is dependent of the method used in its preparation.

McGill University

1980

Electronic Thesis or Dissertation

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