SURVIVAL, BODY-WEIGHT, AND SPONTANEOUS NEOPLASMS IN AD LIBITUM-FED AND FOOD-RESTRICTED FISCHER-344 RATS

Ad libitum-fed (AL) and food-restricted (FR) Fischer-344 male and fema le rats were monitored for survival, body weight, and spontaneous neop lasms. Mean and maximal lifespans for each group were inversely relate d to mean body weights. AL males were the shortest lived (mean lifespa n 101 wk) followed by AL females (118 wk), FR males (125 wk), and FR f emales (132 wk). Gross and microscopic examinations were performed on 851 rats from cross-sectional and longevity components of the study. I n FR groups, the incidence of mammary gland fibroadenomas, testicular interstitial cell tumors, and pituitary neoplasms was decreased while the latency of these neoplasms was increased. In longevity components, most FR groups had a higher incidence of leukemia than AL cohorts, bu t all FR groups had a higher mean age at death for the rats with leuke mia. Higher leukemia rate in the FR groups was thought to be a result of their extended mean lifespan.