AbstractThe aim of this study was to investigate the effects caused by subchronic exposure to diphenyl diselenide in rats. Adult Wistar rats were exposed to diphenyl diselenide (5–300 µmol kg−1, subcutaneously) once a day for 14 days. The subchronic administration of diphenyl diselenide at a dose of 300 µmol kg−1 significantly increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities in plasma. Conversely, this exposure did not alter lactate dehydrogenase (LDH) activity, urea and creatinine levels in plasma. The activity of δ‐aminolevulinate dehydratase (δ‐ALA‐D) from liver and kidney was inhibited by high dosages of diphenyl diselenide. Diphenyl diselenide did not alter renal Na+/K+ATPase. A decline in body weight gain was associated with a decrease in food consumption in rats treated with 100 or 300 µmol kg−1 diphenyl diselenide. At these dosages (100 and 300 µmol kg−1), diphenyl diselenide did not cause histological alterations in the liver of rats. Taken together, these results demonstrated that subchronic exposure to diphenyl diselenide at high doses induced minor toxicological effects. Copyright © 2007 John Wiley & Sons, Ltd.