Effect of selenium compounds on murine B16 melanoma cells and pigmented cloned pB16 cells

The effects of selenium compounds such as sodium selenite, sodium selenate, seleno-DL-cystine and seleno-DL-methionine (100 microM and 10 microM) on B16 and pigmented cloned pB16 murine melanoma cells were investigated in vitro. At the tested concentrations, B16 cells showed a greater sensitivity to the toxic effects of sodium selenite and seleno-DL-cystine than pB16 cells, whereas no decrease of B16 and pB16 cell number was observed after incubation with sodium selenate or seleno-DL-methionine. Glutathione (GSH) percentages were strongly decreased only by selenite and seleno-DL-cystine; it was marked more in B16 than in pB16 cells. The pretreatment of B16 cells with a GSH depleting agent (10 microM buthionine-[S,R]-sulfoximine) did not significantly influence the cytotoxic effects of selenite and seleno-DL-cystine. On both cell populations, GSH preincubation (50 microM) enhanced the cytotoxicity of selenite whereas the survival of seleno-DL-cystine treated cells was increased. Glutathione peroxidase (GSH-Px) activity in B16 cells was more sensitive than in pB16 cells to the activating effect of selenite, and particularly of seleno-DL-cystine: however, cell-free controls indicated that activation was mainly due to glutathione reductase. The rate of 75Se (as sodium selenite) uptake in both cell populations was maximal within the first hour of incubation, with a preferential accumulation in the cytosol; after 24 h of incubation, the amount of 75Se in cytosol and pellet was approximately the same.(ABSTRACT TRUNCATED AT 250 WORDS)