MELATONINS INHIBITORY EFFECT ON GROWTH OF ME-180 HUMAN CERVICAL-CANCER CELLS IS NOT RELATED TO INTRACELLULAR GLUTATHIONE CONCENTRATIONS

The effect of various concentrations of melatonin on the growth of ME- 180 human cervical cancer cells in vitro was examined. Melatonin at a concentration of 2 mM inhibited the growth of the cells after 48 h of melatonin treatment. At concentrations of 2 mu M or 0.1 mM melatonin h ad no effect on cell proliferation, To determine whether the inhibitor y effect of melatonin on the growth of the cervical cancer cells was l inked to intracellular glutathione concentrations, experiments were pe rformed in which intracellular glutathione levels were depressed by th e addition of buthionine sulfoximine to the incubation medium 24 h bef ore the addition of melatonin, The results show that 2 mM melatonin tr eatment still inhibits the growth of cells when glutathione levels are depressed by 95%. Even with depressed glutathione levels, 0.1 mM mela tonin still had no effect on cell growth, Thus, melatonin's ability to inhibit ME-180 cervical cell growth in vitro may be independent of in tracellular glutathione concentrations. It was also found that during one passage the intracellular glutathione levels of cervical cancer ce lls gradually decreases. When 4.5-day-old medium was replaced with new medium, intracellular glutathione levels partially recovered within 3 6 h. This suggests that the observed gradual reduction of cellular glu tathione during incubation was a result of a reduction of some constit uent in the medium after prolonged culture of the cells.