Metabolic activity of cultured tissues. (A) Representative images of 5 μm-thick tissue sections incubated in MTT. Fresh and E2-treated tissues display formazan crystal formation affirming tissue viability, while no crystals formed in damaged tissues. Scale bar, 50 μm. (B) Amount of dissolved formazan crystals measured in a spectrophotometer. In fresh and E2-treated tissues there are equally high amounts of crystals as determined by the absorbance measured, while in damaged tissues the crystal levels are significantly lower (n = 3, *P = 0.05 for damaged versus E2-treated and fresh). Data represent means ± standard deviation.