Effects of food restriction for 3 or 7 days on toxicity-related parameters in rats

In toxicity studies performed during drug development, the secondary effects of decreases in food consumption that are not direct toxic effects may cause incorrect interpretations of toxicologic profiles. Although previous studies have characterized the effects of reductions in food intake on toxicological parameters in rats, these were conducted for ≥2 weeks, making it difficult to determine whether changes in toxicity-related parameters are secondary to a reduction in food intake or compound effects in the short-term studies conducted in the early stages of drug discovery. Therefore, we evaluated the effects of low food intake for 3 or 7 days on toxicity-related parameters. Male and female rats were fed ad libitum (control group) or at 80%, 60%, or 40% of the mean pre-measured food intake for each group for 3 or 7 days, and their general condition, body weights, water consumption, quantitative urinalysis parameter, hematology, blood chemistry, myelogram, organ weights, histopathology were evaluated. Similar to the previous studies of food restriction of ≥2 weeks, there were decreases in the reticulocytes and leukocytes on hematology and in erythroblasts and myelocytes on a myelogram, especially in their later stages of differentiation, after 7 days of food restriction. Furthermore, natriuresis, which develops in fasted humans, was also identified after 7 days of food restriction. The present study is the first to identify changes in toxicity-related parameters during short-term food restriction. The perspective obtained from this study should aid in the future interpretation of the toxic effects of compounds that cause reductions in food intake.