[Is the estimation of the activity of MTT-reduction suitable for the determination of basal cytotoxicity?].

The influence of 19 substances on the reduction of thiazolyl-blue (MTT) by cultivated calf aortic endothelial cells was studied. The substances tested could be classified into three groups. The first one includes drugs without significant effect on the reduction of MTT, the second one inhibits these reaction only weakly (less than 50%) and 10 substances of the third group showed an inhibition rate greater than 50%. There is no statistical reliability in the correlation between the IC50-values of the substances studied in the MTT-test and their LD50-values (mouse, per os). The MTT-test does not permit the estimation of the basal cytotoxicity but only the inhibition of the activity of succinate dehydrogenase and the cytochrome c/c1-complex of the respiration chain of cultivated endothelial cells.