Aluminum ions stimulate mitosis in murine cells in tissue culture

Addition of aluminum to the culture medium of Nakano mouse lens epithelial (NMLE) cells and Swiss 3T3K cells induced both 3H-thymidine incorporation and mitosis. This is in contrast to other metal ions such as vanadium, which, at concentrations high enough to increase 3H-thymidine incorporation, actually inhibits mitosis (Jones and Reid, J Cell Physiol 121:199, 1984). Aluminum concentrations between 20 microM and 50 microM were most effective. The 3T3 cells respond to aluminum with a 7.6-fold increase, and NMLE cells respond with a 21-fold increase in 3H-thymidine incorporation. DNA synthesis in NMLE cells was also found to be synergistically stimulated by aluminum and low concentrations of insulin (4.5 X 10(-8) M). A 3.25-hr incubation with 50 microM aluminum was sufficient to induce 50% of maximum 3H-thymidine incorporation during the 40-hr assay. Aluminum-stimulated 3H-thymidine incorporation is inhibited by hydroxyurea, and aluminum causes an increase in cell number. Also, by sedimentation equilibrium analysis of the product of aluminum-stimulated DNA synthesis it was found that a single copy of DNA was synthesized following addition of aluminum to quiescent cells. These facts indicate that aluminum induces both S-phase DNA synthesis and mitosis. However, only 48% of the NMLE cells found to be labeled with DNA went on to divide. In contrast, although only a small percentage of 3T3 cells were found to be labeled after aluminum treatment, all of these cells appeared to go through mitosis.