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

A chemical method for the separation ofheme and nonheme iron-containing fractions in mouse tissues has been used tostudy the uptake of ⁵⁹Fe into both theheme and nonheme iron fractions inspleen and femoral bone marrow, in orderto investigate the possible relationshipsbetween the total uptake into spleen tissue and the rate of uptake into the hemefractions. In control mice, only aboutone third of the ⁵⁹Fe is directly associated with heme during the first dayafter administration, and this fraction decreases as radioactive red cells are released from the spleen into blood. Tendays 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 750rads. A similar alteration in the proportion of ⁵⁹ Fe in the spleen haem fractionoccurred in mouse radiation chimeras asthe dose of injected syngeneic bonemarrow cells was reduced from 5 x 10⁵to zero. Similar results were found infemoral bone marrow. These results indicate that in this system the rate of uptake into whole tissue is not a measureof the uptake into heme; it is necessary,therefore, to use the method involvingthe measurement of iron uptake intoheme, rather than the total tissue uptake,when estimating hemoglobin synthesisor erythropoiesis.

Submitted on February 15, 1971 Revised on April 5, 1971 Accepted on April 8, 1971