Marrow cell injury following Ca45 uptake in bone: changes in marrow and peripheral blood cellularity.

The amounts of Ca45 used in these experiments were small and the calculated radiation doses through the first 6 days when the most drastic hematologic changes were observed were low compared to x-ray doses used in other experiments to perturb the normal steady state of the bone marrow. Nevertheless, the changes produced within the bone marrow in these rats receiving Ca45 were as great, or greater in some instances, as those caused by larger x-ray doses.Radiation from Ca45 incorporated into the bones of the rats, caused cell death and accelerated cell removal within the mature marrow granulocyte pool. Mitotic delay or inhibition of the rapidly dividing and differentiating precursor cells plus the radiation-induced cell death caused a rapid and extensive decrease in the number of nucleated cells of the marrow.Since there were fewer mature cells in the marrow to cope with natural attrition rates in the peripheral blood, granulocytopenia resulted. Being unable to deliver mature cells for circulation, the marr...