OBJECTIVECardiotonic steroids (CTS) can bind to Na+, K+ -ATPase to activate complex intracellular signaling cascades regulating the proliferation and apoptosis of cells. The aim of this study was to investigate the effects of ouabain at different concentrations on growth regulation in various kinds of leukemia cell lines and explore the pathogenesis of leukemia, the functions of Na+, K+ -ATPase as a signal transduction conductor and its effects on cell growth.

METHODSUsing the MTT assay, the survival rates of leukemia cell lines were observed 6, 12 and 24 hrs after treatment with 1 or 10 nmol/L ouabain. The expression of Na+, K+ -ATPase alpha1 subunit of leukemia cells was detected by Western blot.

RESULTSThe MTT results showed that ouabain at 1 nmol/L or 10 nmol/L induced proliferation of lymphocytic leukemia B95 and Jhhan cell lines, as well as megakaryocytic leukemia M07e and Meg01 cell lines. Ouabain at 1 nmol/L or 10 nmol/L increased the expression of Na+, K+ -ATPase alpha1 subunit. There were significant differences in the proliferation and the expression of Na+, K+ -ATPase alpha1 subunit of the leukemia cell lines between the ouabain treatment and the blank control groups 24 hrs after ouabain treatment (P<0.05). The proliferation effect of leukemia cell lines was in a direct proportion with the ouabain concentration and incubation time.

CONCLUSIONSNa+, K+ -ATPase plays an important role in signal transductions. Through binding to ouabain, Na+, K+ -ATPase may regulate proliferation of leukemia cell lines of different origins. Ouabain at 1 nmol/L or 10 nmol/L may induce proliferation of lymphocytic leukemia cell lines (B95, Jhhan) and megakaryocytic leukemia cell lines (M07e, Meg01), and the proliferation effect was in a direct proportion with the concentration and incubation time of ouabain.