An X-ray microanalysis study of cation changes during development in erythropoietic cells

Abstract

The change from high potassium (HK) stem cells to low potassium (LK) red blood cells which occurs during erythropoiesis in the dog has been investigated by electron probe x-ray microanalysis of single cells. The intracellular elemental concentrations of potassium, sodium and iron were determined: 1) in the reticulocytes of peripheral blood from dogs with experimentally and naturally accelerated erythropoiesis, using wavelength-dispersive spectrometry of intact single cells; and 2) in the various erythropoietic cells of normal, adult dog marrow, using energy-dispersive spectroscopy of quench-frozen cryosections. The former experiments demonstrated that the switch from HK to LK cell type, which occurs during or slightly before denucleation of the orthochromatophilic erythroblast, is clearly correlated with a decrease in potassium concentration and also with the bulk of hemoglobin synthesis. The studies using cryosectioned preparations of normal dog confirmed a similar, negative correlation between sodium and potassium, although in this case only the onset of iron accumulation could be detected in the nucleated cells. When combined with the morphological information available from cryosections, it is concluded that the most immature erythroid cells are HK cells (CK greater than 80 mmols/kg wet-wt.), whereas a majority of the later erythroid cells were of the LK variety (CK less than 10 mmols/kg). This indicates that in normal dogs, the switch from HK to LK type occurs mainly in the basophilic erythroblasts.