The number of viable cells in each well was also
estimated bythe uptake of thetetrazolium salt,3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide (MTT). MTT, selectively taken up by mitochondria, is converted to a dark-blue product by living, but not by
dead, cells. After the induction of quiescence in 96-well plastic culture
dishes at the density of 1*10^3cells/well, the cells were incubated withthe indicated drugs for 24 h. Subsequently, 20μL of MTT (2.5 g/L) was added to each well, and the incubation was continued for an additional
4 h at 37C. Thereafter, 150μL of DMSO was added to each well, and
an absorbance at 490 nm was read on a microplate reader