Extracorporeal irradiation of the blood in a rat model for human acute myelocytic leukemia. Comparative evaluation of three treatment regimens with emphasis on cell compartment analysis

Results of three different regimens of extracorporeal irradiation of the blood (ECIB) are compared (1 X 20,2 X 10, and 4 X 5hr) in a rat model for human acute myelocytic leukemia. The D0 for X rays of leukemic cells in the blood was 68 cGy. The transit dose varied from 380 to 660 cGy. Evaluation was performed by follow-up of the number of peripheral leukemic cells (and lymphocytes) and quantitative cell compartment analysis by measuring the distribution of infused 51Cr-labeled leukemic cells. Repeated sessions of ECIB (2 X 10 hr; 4 X 5 hr) proved far more effective in terms of cell depletion than one long session (1 X 20 hr). Chromium studies indicated that the sizes of the blood compartments and of the rapidly exchangeable tissue pool are markedly reduced (maximally by about 70%). The more-sessile organ compartments are only slightly influenced. It appeared that the traffic of leukemic cells is subject to a regulatory mechanism. The more the peripheral compartment is depleted, the more cells are mobilized from the rapidly and slowly exchangeable tissue compartments