The correlation of composition and morphology during the high to low potassium transition in single erythropoietic cells.

The change from high potassium dog erythroid cells to low potassium red blood cells during erythropoiesis was investigated by X-ray microanalysis of single cells. A correlation of morphology and composition, using freeze-dried cryosectioned preparations, showed that during normal erythropoiesis in dog bone marrow the switch from high potassium to low potassium occurs during the change from early to late nucleated erythroid cells, and in synchrony with the beginning of iron accumulation. In contrast, during rapid erythropoiesis in dogs with phenylhydrazine-induced anemia, the most prominent change in cation composition as well as the accumulation of iron occurs during the reticulocyte stage in the peripheral blood. The determination of the absolute amounts of sodium and potassium per cell in stress reticulocytes of peripheral blood indicated that the changeover from high potassium to low potassium actually occurs by the loss of cellular potassium during volume reduction, with little change in the amount of cellular sodium. This suggests that maturation may involve a selective change in potassium permeability. Lastly, it was observed that not all cells followed the predominant pathway with respect to change in morphology, membrane permeability and hemoglobin synthesis. One particular subpopulation appeared to follow a sequence which expressed the complete HK to LK transition before the accumulation of any iron; this implies the possibility of completing protein synthesis in a low potassium intracellular milieu.