Aim: To investigate the histology and function of the kidney in mice exposed to diff erent concentrations of phenol through the gavage method for 10 consecutive days. Materials and methods: Forty female BALB/c mice were selected and randomly divided into 1 control group and 3 experimental groups. Th e control group was administered distilled water through the gavage method, while the experimental groups received daily doses of 80, 180, and 320 mg/kg of phenol, respectively. Aft er 10 days, blood samples were collected and the sera were analyzed biochemically. Renal tissue samples were also taken and histopathological changes of the kidneys were examined using optical and electron microscopes. Results: No signifi cant diff erences were found in the serum levels of sodium, potassium, chloride, bicarbonate, or total protein in all of the phenol-treated mice in comparison with the control group. Th e levels of creatinine and blood urea nitrogen and the activity of alkaline phosphatase in the sera of the phenol-treated mice showed a signifi cant increase in comparison with the control group (P < 0.05). Histological changes including renal tubules necrosis, interstitial lymphoplasmacytic nephritis, and hyperemia were observed. Th e ultrastructural changes included reduction in the number and size of microvilli in the epithelial cells of the proximal convoluted tubules (PCTs), deformation and shrinkage of the nuclei, malformation of the mitochondria and folding of the cytoplasm in the epithelial cells of the PCTs, dilation of the urinary space in the renal corpuscles, and formation of endothelial electron-dense deposits in the basement membranes of the glomeruli. Conclusion: Based on the fi ndings, it is concluded that the observed signifi cant increases of serum creatinine levels, blood urea nitrogen levels, alkaline phosphatase activity, and histopathological changes in the kidneys of phenol-treated mice indicate tissue injury. Th ese fi ndings suggest
