Variations in the Relationships Between Total 59Fe Uptake and the Uptakes Into Heme and Nonheme Fractions of Spleen and Bone Marrow in Irradiated Mice and Mouse Radiation Chimeras

Abstract

Abstract A chemical method for the separation of heme and nonheme iron-containing fractions in mouse tissues has been used to study the uptake of 59Fe into both the heme and nonheme iron fractions in spleen and femoral bone marrow, in order to investigate the possible relationships between the total uptake into spleen tissue and the rate of uptake into the heme fractions. In control mice, only about one third of the 59Fe is directly associated with heme during the first day after administration, and this fraction decreases as radioactive red cells are released from the spleen into blood. Ten days after X-irradiation of mice, the proportion of 59Fe in the spleen heme fraction 6 hr after intraperitoneal administration decreased from about 30 to 10% of the total splenic activity as the radiation dose was increased from 500 to 750 rads. A similar alteration in the proportion of 59 Fe in the spleen haem fraction occurred in mouse radiation chimeras as the dose of injected syngeneic bonemarrow cells was reduced from 5 x 105 to zero. Similar results were found in femoral bone marrow. These results indicate that in this system the rate of uptake into whole tissue is not a measure of the uptake into heme; it is necessary, therefore, to use the method involving the measurement of iron uptake into heme, rather than the total tissue uptake, when estimating hemoglobin synthesis or erythropoiesis.