Continuous intravenous infusion in athymic (nude) rats: an animal model for evaluating the efficacy of anti-cancer agents

The athymic (nude) rat (rnu/rnu) has been used for a number of years in res earch into various human tumours involving xenotransplantation. We now repo rt the validation of a continuous intravenous infusion method in nude rats using a tail cuff tether, which enables the study of the efficacy of novel anti-cancer materials in this mutant strain, using intravenous infusion and with no restriction of the animals or of the tumour implantation sites by jackets. Ten animals each had a cannula surgically implanted into the vena cava via the femoral vein and exteriorized via a tail cuff. Animals were housed sing ly in conventional cages following surgery. Following a recovery period of 5 days all animals were continuously infused with physiological saline at a n infusion rate of 0.5 ml/h for a further 37 days. Body weights and food co nsumption were recorded weekly. Blood samples were taken approximately 14 d ays post-surgery and analysed for haematology and clinical chemistry parame ters. All animals were successfully cannulated, and no unexpected adverse c linical signs were noted during the recovery period and the 37 days of infu sion. The results demonstrate that it is possible to surgically cannulate the fem oral vein of athymic (nude) rats and infuse them in conventional cages for a period of up to 37 days with minimal adverse effects. The minimal restrai nt required provides benefits both to the animal and to the conduct of stud ies such as assessment of tumour growth in the absence of a jacket. Recent work has demonstrated that the same techniques can be successfully applied to the nude mouse.