Minimal Bone Marrow Damage in Mice Given Bleomycin¹

The effects of bleomycin on several parameters of hematopoiesis were studied. Large single or repeated doses of from 0.5 to 3 mg/mouse were given to normal mice at various times before irradiation and/or marrow donation.

A single injection of 2 mg bleomycin caused no change in the total number of nucleated cells per humerus, but when cells from these humeri were injected into lethally irradiated recipients, there was a decrease in spleen weight, ⁵⁹Fe uptake, and colony numbers, compared with 0.9% NaCl solution-injected controls. When donor mice were given 3 daily injections of 1 mg bleomycin and were killed 2, 5, 7, 9, and 12 days later, the mean numbers of blood lymphocytes and nucleated cells per humerus were reduced. Recipients of marrow from these mice had both lower spleen weight and ⁵⁹Fe uptake and fewer colonies 8 days after irradiation than did recipients of control cells. These reductions were small (minimal values were > 30% of control), but they persisted and even became somewhat larger as the interval after injection of bleomycin increased through 12 days.

The effects of combining bleomycin with irradiation were similar. Colony number, spleen weight, and spleen ⁵⁹Fe were reduced but did not fall below 37% of control. At most of the doses of bleomycin and times of injection relative to irradiation used in these experiments, some decrease in the hematopoietic parameters was observed. However, no consistent relationship of these alterations to dose or time of administration was seen. Thus, bleomycin has minimal but definite effects on those parameters of murine hematopoiesis measured in these experiments.