Effects of food restriction on reproductive and toxicological parameters in rats--in search of suitable feeding regimen in long-term tests.

Eighty Sprague-Dawley rats, consisting of 40 animals of each sex, were examined for age-related lesions after a 13-week food restriction. From 6 weeks of age, four groups of 10 male and 10 female rats each were fed normal pelleted chow, ad libitum for the control group and approximately 85%, 70% and 55% of feed consumption in the control group, for 13 weeks. Estrous cycles in females were examined during the 3rd through 12th week of the study, and hematological, blood biochemical and pathological examinations of all animals were carried out after the 13-week feeding. Estrous cycles were prolonged or stopped in most females of the 55% feeding group from the 7th week of restricted feeding and atrophy of the theca granulosa cells with decreased cytoplasmic lipid droplets was found in the ovaries at necropsy. In the males of the 55% feeding group, Leydig cell atrophy was found in the testes. The groups at 70% and 85% feeding showed no abnormality in hematological, blood biochemical and pathological observations. On the other hand, decreases in plasma lipid peroxide levels were noted in the 70 and 85% feeding groups. These results suggest that 70% and 85% feedings seem suitable for minimizing development of age-related changes without nutritional disorders.