Study of maturation of membrane transport function in red blood cells by X-ray microanalysis.

Red blood cells of certain species of animals, such as dogs and cats contain low potassium and high sodium, whereas the erythropoietic stem cells giving rise to these cells are of high potassium type. This paper examines the sequence of membrane transport changes during erythropoiesis by analyzing the K, Na and Fe in single bone marrow cells, reticulocytes and mature red blood cells with X-ray microanalysis. The relationship between K/Na ratios and Fe/(K + Na), which is analogous to hemoglobin concentration, gives an index of maturation stage. The relationships between K/Na and Fe/(K + Na) in the marrow cells of normal adult dog and those of a phenylhydrazine-injected dog with accelerated erythropoiesis show that the modification of cation composition occurs after the initiation of hemoglobin synthesis but before its completion. Similar relationships in the reticulocytes obtained from phenylhydrazine-injected dogs as well as from newborn dogs show a consistent decrease in K/Na with increased Hb, indicating a drastic change in cation composition during the maturation of the reticulocytes. Therefore the modification in membrane transport function must have occurred before or during the formation of reticulocytes.