Menadione metabolism to thiodione in hepatoblastoma by scanning electrochemical microscopy.

The cytotoxicity of menadione on hepatocytes was studied by using the substrate generation/tip collection mode of scanning electrochemical microscopy by exposing the cells to menadione and detecting the menadione-S-glutathione conjugate (thiodione) that is formed during the cellular detoxication process and is exported from the cell by an ATP-dependent pump. This efflux was electrochemically detected and allowed scanning electrochemical microscopy monitoring and imaging of single cells and groups of highly confluent live cells. Based on a constant flux model, approximately 6 x 10(6) molecules of thiodione per cell per second are exported from monolayer cultures of Hep G2 cells.