Effect of ischemic conditioning on oxidative stress, autophagy and apoptosis in the kidney. 4-hydroxynonenal (4-HNE, A-D) immunostaining of rat kidney sections. The kidneys with different treatment were immunostained with anti-4-HNE antibody. There is no 4-HNE immunoreactivity (brown color) present in the sham control kidney section (A). The 4-HNE immunoreactivity is present in both proximal and distal tubules of the 15 × 4 (B) and 60 × 1 (D) kidney. A less 4-HNE immunoreactivity is indicated in the 30 × 2 kidney (C). There is little stain of autophagy (E) and no apoptosis formation (I) in the sham control kidney. In response to I15 × 4, I30 × 2 or I60 × 1 treatment, all renal proximal and distal tubular autophagy (brown color, F-H) and apoptosis (brownish nuclei, J-L) are displayed in the insulted kidney. However, the mean data of 4-HNE stain (M), autophagy formation (N) and apoptosis production (O) were displayed in an order of 60 × 1 > 15 × 4 > 30 × 2 > sham control. * P < 0.05 vs. sham control (control) kidney. # P < 0.05 vs. 60 × 1 group.