Effects of food restriction on toxicological parameters in juvenile rats.

To examine the effects of decreased food consumption on toxicological parameters in juvenile rats, rats on postnatal day 21 were fed 40%, 50% (only four weeks), and 60% less food, compared to that of controls for four or eight weeks, and clinical observations, measurement of body and organ weights, morphological differentiation analysis, clinical pathology, and macroscopic and microscopic examinations were conducted. The body weight decreased depending on the degree of food restriction (FR). Cleavage of the balano-preputial skinfold was delayed, and cell debris in the epididymal lumen was noted as a related finding after four-week FR. Vaginal opening was also delayed, and some histopathological findings, such as absence of corpus luteum in the ovary, mucinous degeneration in the vagina, and immature uterus, were noted after eight-week FR. Erythrocyte count increased after four-week FR, but slightly decreased in males only after eight-week FR, and decreased leukocyte and/or reticulocyte counts, accompanied by related histopathological findings were noted after four- and eight-week FR. In blood chemistry, the levels of total protein including globulin, glucose, triglyceride, and calcium decreased, and sodium and chloride increased after four- and eight-week FR. Increases in activities of aspartate transaminase and lactate dehydrogenase and total bilirubin levels were noted after four-week FR, which were attenuated after eight-week FR. The effects of FR seemed to be more remarkable after four weeks. In drug safety evaluation, findings caused by malnutrition should be considered in juvenile toxicity studies when decreased food consumption is observed.