Dose-response for Hg2+-induced cell death. Animals were treated with Hg2+ (0.875 and 1.75 mg/kg, ip) for 24 h and the left kidneys were infused with ethidium homodimer. Cryosections of the kidneys were then fixed, permeabilized and labeled with DAPI as described in the Methods section. Panels A, D, G are images from 0.9% NaCl vehicle control-treated animals. Panels B, E, H are from 0.875 mg/kg Hg2+-treated animals, and panels C, F, I are from 1.75 mg/kg Hg2+-treated animals. Panels A-C show phase-contrast images of the same fields in D-F and G-I, respectively. D-F show total nuclei labeled in each field by DAPI fluorescence, G-I show nuclei labeled by ethidium homodimer. The scale bar in the top left image represents 100 μm.