MARROW CELL INJURY FOLLOWING Ca⁴⁵ UPTAKE IN BONE

¹ From the Johns Hopkins University, School of Hygiene and Public Health, Department of Radiological Sciences, Baltimore, Maryland

The effects of Ca⁴⁵ on the cells of the bone marrow in the rat were studied. Animals in 5 groups received injections of 25 µc, 50 µC, 100 µc, 200 µc, and 300 µc of Ca⁴⁵, respectively. They were sacrificed at 12 hours, 24 hours, 36 hours, 2 days, 4 days, 6 days, 8 days, 12 days, 19 days, 25 days, and 32 days, and the bone marrow was removed from the tibiae and assayed for damage. The incidence of micronuclei and the changes in the mitotic index were used as an indication of radiation damage to the nucleus.

The following results were obtained: A generally linear increase in micronuclei was observed with increasing activity of Ca⁴⁵. Doses as low as 50 µc produced a 2.92 fold increase in micronuclei. Within the first 4 days after injection of the isotope, bone marrow from animals receiving a 300 µc dose showed about 5 times as many micronuclei as controls. When the animals treated with 25 µc were observed at 12, 24, 36, and 48 hours after injection, 4.75, 5.63, 3.00, and 1.69 fold increases, respectively, were noted in micronuclei. The mitotic index of the bone marrow cells from all treated animals remained below normal throughout the experiment and at the 32nd day was still from 2.4 to 5.1 times lower than the controls.

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