An improved MTT assay using the electron-coupling agent menadione.

A modification of the MTT based tetrazolium colorimetric assay is described. Using the electron-coupling agent menadione formazan formation by murine splenocytes and P-815 cells was significantly increased whereas dye reduction by macrophages was hardly influenced. These observations suggest that it should be possible to improve the tetrazolium based cytotoxicity assays of murine macrophages against cells of the syngeneic tumour cell line P-815.