Inhibition of normal granulopoiesis by cytostatic agents.

Rabbits were treated with cyclophosphamide and 5-fluorouracil, myelosuppressive cytostatic agents, applied with a single dose of 1/3 LD50 or daily doses of 1/30 LD50 given for 14 days. Functional tests for evaluation of granulopoiesis were regularly performed at standard intervals and were following: leukocytosis, bone marrow picture with mitotic index, 3H-thymidine incorporation in vitro followed by autoradiography of labeled promyelocytes and myelocytes, serum lysozyme activity, mobilization of granulocyte reserve pool by staphylococcal alpha-toxin, cytochemistry of granulocytes, phagocytosis ability and Nitro-BT reduction. It has been found that 6-10 days after application of cytostatics, a marked depression of proliferation of young granulocyte forms and lowered reserve pool, are regularly observed. This was followed by spontaneous regeneration of granulopoiesis. No changes were noted in functional tests of mature granulocytes in peripheral blood. It is suggested that for investigation of the impairment of granulopoiesis after application of cytostatic agents, most suitable is evaluation of mobilization of the bone marrow reserve pool, lysozyme activity in blood serum and labelling of promyelocytes and myelocytes with 3H-thymidine in vitro.