Effects of Repeated Intraperitoneal Injection of Pharmaceutical-grade and Nonpharmaceutical-grade Corn Oil in Female C57BL/6J Mice

Due to potential adverse effects on animal wellbeing, the use of nonpharmaceutical-grade substances in animal research must be scientifically justified in cases where a pharmaceutical-grade version of the substance exists. This requirement applies to all substances, including vehicles used to solubilize experimental drugs. To date, no studies have evaluated the direct effect of the pharmaceutical classification of a compound on animal wellbeing. In this study, we evaluated intraperitoneal administration of pharmaceutical-grade corn oil, nonpharmaceutical-grade corn oil, and saline in female C57BL/6J mice. Compounds were administered every 48 h for a total of 4 injections. Mice were evaluated clinically by using body weight, body condition score, visual assessment score, CBC, and serum chemistries. Animals were euthanized at 24 h and 14 d after the final injection. Inflammation of the peritoneal wall and mesenteric fat was assessed microscopically by using a semiquantitative scoring system. Saline-dosed groups had lower pathology scores at both time points. At day 21, pharmaceutical-grade corn oil had a significantly higher pathology score compared with nonpharmaceutical-grade corn oil. No other significant differences between the corn oil groups were observed. The use of nonpharmaceutical grade corn oil did not result in adverse clinical consequences and is presumed safe to use for intraperitoneal injection in mice. Differences in inflammation between the 2 groups suggest that the use of either pharmaceutical-grade or nonpharmaceutical-grade corn oil should be consistent within a study.