THE MTT TETRAZOLIUM SALT ASSAY SCRUTINIZED - HOW TO USE THIS ASSAY RELIABLY TO MEASURE METABOLIC-ACTIVITY OF CELL-CULTURES IN-VITRO FOR THEASSESSMENT OF GROWTH-CHARACTERISTICS, IC50-VALUES AND CELL-SURVIVAL

The methylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay is widely used for in vitro measurement of the metabolic viability of cel l cultures subjected to different culture conditions. This convenient assay, which is based on the ability of viable cells to produce formaz an, can be affected significantly by a number of conditions. These con ditions can be roughly divided into two groups, firstly influences whi ch affect the spectrum of the produced formazan and secondly influence s which affect the amount of formazan produced per cell. We studied th e various chemical and biochemical aspects involved in the MTT assay. Our data indicate that microscopical viewing of cell cultures before a nd after performing the assay, a medium renewal with a well-defined MT T-incubation medium at the end of the culture period and regular cell counting are essential steps to ensure a reliable performance of the M TT assay. In conclusion, providing the necessary precautions are taken , the MTT assay can be used reliably to measure metabolic activity of cell cultures in vitro for the assessment of growth characteristics, I C50-values and cell survival.