(A) Ischemic injury of the kidney elevated sCr at the 24-hour time point (P = NS; control n = 16, ischemia n = 13) but had no effect on BUN (P = NS) or hematocrit (HCT; P = NS). Volume depletion (volume depletion) elevated sCr 3-fold (P < 10–5; volume depletion n = 14), BUN 3-fold (P < 0.001; control n = 11, volume depletion n = 11), and HCT 1.5-fold (P < 0.01; control n = 6, volume depletion n = 11). Ischemia differed from volume depletion in all 3 parameters. Significance was determined by Student’s 2-tailed t test. P values were Bonferroni corrected. Data represent mean ± SD. Bars = 100 μm. PVC, packed volume of cells. (B) Renal artery ischemia generated focal coagulative necrosis of tubules (*) while volume depletion failed to demonstrate evidence of extensive kidney damage. H&E stain. Bars = 100 μm. (C) Renal artery ischemia generated TUNEL+ cell death (green) throughout the cortico-medullary junction and medulla, whereas volume depletion had little effect, except for a few scattered cells in the medulla. TUNEL was assayed by Click-iT Plus TUNEL kit (Invitrogen). Bars = 100 μm. (D) Urinary tubular injury markers Kim-1 and Ngal were induced by ischemic injury in a dose-dependent fashion but demonstrated limited responses to prolonged volume depletion (3 days) despite higher sCr levels. Urine Ngal and Kim-1 were quantified by ELISA (mouse Ngal: R&D Systems MLCN20; mouse Kim-1: R&D Systems MKM100) (n = 4) and compared with normal control. (A and D) *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.00001 (2-tailed Student’s t test). P values were Bonferroni corrected. The box plots depict the minimum and maximum values (whiskers), the upper and lower quartiles, and the median. The length of the box represents the interquartile range.