AbstractThe simple organoselenium compound diphenyl diselenide (PhSe)2 is a promising new pharmacological agent. However, few toxicological evaluations of this molecule have been reported. We evaluated the effects of acute administration of (PhSe)2 on toxicological parameters in rabbits. Adult New Zealand rabbits were exposed to (PhSe)2 (5–500 µmol kg−1, intraperitoneally) once a day for 5 days. Exposure to 500 µmol kg−1 caused 85% mortality. Exposure to 50 µmol kg−1 of (PhSe)2 increased the glutathione levels in the hippocampus, kidney, heart, muscle and blood, whereas lipoperoxidation (TBARS) decreased in the cerebellum and kidney after exposure to 5 µmol kg−1. The activity of glutathione peroxidase increased in the heart and muscle of rabbits treated with 50 µmol kg−1 of (PhSe)2 and glutathione reductase activity was reduced in the cerebellum, cerebral cortex and kidney. Treatment with (PhSe)2 reduced the activity of δ‐aminolevulinate dehydratase in the hippocampus and increased this activity in the heart, but did not alter the activity of complexes I and II of the respiratory chain in the liver and brain. Hepatic and renal biochemical and histological parameters were not modified by (PhSe)2 and apoptosis was not detected in these tissues; however, the hepatic cells tended to accumulate fat vacuoles. These results indicated that acute toxicology to (PhSe)2 in rabbit is dependent on the dose, which should motivate further experiments on the therapeutic properties of this compound. Copyright © 2010 John Wiley & Sons, Ltd.