EARLY PROGRESSION FROM DIMETHYL SULFOXIDE‐INDUCED G 0 /G 1 ARREST IN L 1210 CELLS

Recently, dimethyl sulfoxide (DMSO) has been used as a convenient cryoprotectant for stem cells in stem cell transplantation using allogenic peripheral blood or umbilical cord blood. As the stem cells have a multipotency, clarification of the extent of cell proliferation after transplantation is difficult. In the present study, DMSO gradually induced G 0 /G 1 arrest in mouse leukemia L 1210 cells with good cell viability. After removal of DMSO, the cells proliferated appropriately, resulting in expression of the DNA‐synthesizing enzymes thymidylate synthase and thymidine kinase within 6h, and the cells entering into S phase within 12h. The sequence was followed by the marked activation of both enzymes within 24h and the increase of bromodeoxyuridine (BrdU) immunoreactive (S phase) cells with rapid cell proliferation within 36h. In conclusion, mouse leukemia L 1210 cells, which were treated with 1.5% DMSO for 96h, tolerated the treatment and reversed the cell cycle arrest within 36h.