Adverse effects of tribromoethanol as used in the production of transgenic mice.

Tribromoethanol is widely used as an anaesthetic agent for embryo-transfer surgery for the generation of transgenic mice. Potential side effects such as local irritation, fibrous adhesions in the abdominal cavity, and mortalities of unknown cause have been reported. Mice of three different strains (CD-1, OF-1, NMRI) received intraperitoneal injections of pentobarbiturate (60 mg/kg, 0.4%), tribromoethanol (240 mg/kg, 1.2%), tribromoethanol (450 mg/kg, 2.5%), ketamine/xylazine (120 mg/kg, 1.2%/16 mg/kg, 0.16%) or saline (NaCl, 0.9%). After 24 h the animals were sacrificed and blinded histopathological examination of abdominal organs was performed by light microscopy. Tribromoethanol caused focal to diffuse necrosis primarily of subperitoneal muscle fibres of the abdominal wall, and, occasionally, necrotic changes on the surface of abdominal organs. These changes were associated with acute peritoneal inflammation and fibrinous serositis of the abdominal organs. The severity of the findings increased with the concentration of tribromoethanol. The use of ketamine/xylazine yielded a comparable success rate in embryo transfer without undesirable side effects. Further use of tribromoethanol is not recommended.