Effects of Hg2+ on ethidium-labeling in the renal cortex. Animals were treated with Hg2+ (3.5 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 high-powered (HP) images from control animals and panels B, E, H are from 3.5 mg/kg Hg2+-treated animals. Panels C, F, I represent low-powered (LP) images from 3.5 mg/kg Hg2+-treated animals. Panels A-C show phase-contrast images of the same fields in D-F and G-I, respectively. Panels D-F show total nuclei labeled in each field by DAPI, G-I show labeled nuclei by ethidium homodimer. The white arrow in panel I indicates the boundary between inner medulla and the renal cortex. The scale bar in the top left image represents 100 μm and the scale bar in the top right image represents 500 μm.