POPULATION CHANGES OF A RAT LEUKEMIA BY DIFFERENT ROUTES OF TRANSPLANTATION

Cytologic characteristics of 4 sublines of a transplantable myeloblastic leukemia in rats, DBLA-6, originally induced by 1-butyl-1-nitrosourea in a female Donryu rat were compared. The original cell line showed a gradual change in chromosome constitution from a diploid (44) to tetraploid (81–84) range during serial intraperitoneal (ip) passages. By repeated intravenous (iv) passages, however, the ploidy was converted from tetraploid (83) to diploid (42). The iv-passaged sublines (GV and KV) showed a greater affinity to proliferate in the bone marrow, as indicated by a prominent increase in the leukocyte count in the peripheral blood and by higher percentages of tumor take after iv inoculation of a small number of cells, when compared with the ip-passaged sublines (GP and KP). Such cytologic changes in a cell population by different routes of passage may be the result of adaptive proliferation of either diploid cells in the bone marrow or tetraploid cells in the peritoneal cavity. Successful isolation of diploid sublines from the ippassaged subline by single cell transplantation, which showed characteristics similar to those of the iv-passaged subline, indicated that the diploid cells existed in the original cell population independent of the tetraploid cells and proliferated more in the bone marrow, with greater leukemia-inducing capacities. © 1974 Oxford University Press. All rights reserved.