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The Role of Endocytosis in Transferrin Uptake by Reticulocytes and Bone Marrow Cells
Author(s) -
Hemmaplardh Deeporn,
Morgan E. H.
Publication year - 1977
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/j.1365-2141.1977.tb05758.x
Subject(s) - transferrin , endocytosis , transferrin receptor , bone marrow , chemistry , microbiology and biotechnology , biochemistry , biology , cell , immunology
S ummary . The aims of the work described in this paper were to investigate the process by which transferrin enters immature erythroid cells, to determine whether entry of transferrin into the cells is required for iron utilization by the cells and to see whether substances in the medium surrounding the cells enter the cells along with transferrin. The kxperiments were performed using rabbit transferrin, rabbit reticulocytes and rabbit bone marrow cell suspensions. The process of transferrin uptake was studied by electron microscope techniques using autoradiography of 125 I‐labelled transferrin or transferrin conjugated to ferritin or horseradish per‐oxidase. The results confirmed that transferrin enters reticulocytes and showed that the protein also enters nucleated erythroid cells of the bone marrow but very little is taken up by platelets, cells of the white cell series in the bone marrow or peripheral blood or mature erythrocytes. The two stages of transferrin uptake by erythroid cells, initial absorption and progressive uptake, were shown to be represented morphologically by binding of transferrin to the outer cell membrane, probably to specific receptors, and entry into the cells by endocytosis, respectively. Reticulocytes were unable to utilize 59 Fe for haem synthesis when the 59 Fe was on transferrin which was bound to agarose, Enzacryl AA or Latex beads so that it would not enter the cells. The uptake of transferrin by reticulocytes was not accompanied by uptake of 14 C‐polyethylene glycol dissolved in the medium.