The tetrazolium dye assay for rapid in vitro assessment of cytotoxicity.

The intracellular reduction of a tetrazolium salt (MTT) to a purple formazan is an indicator of cell viability. The MTT test represents a simple colorimetric method to determine cytotoxicity. The present paper describes a new method for solubilisation of the formazan crystals, which makes the assay simpler, more rapid and more reproducible. Different cell lines show different kinetics of formazan formation stressing the need for individual calibration curves. The clear-cut discrimination between cells resistant and non-resistant against oxazaphosphorines indicates that the assay has predictive value for in vivo drug sensitivities. It is concluded that the MTT test is a useful addition to anticancer compound screening programs.