The aging AXC/SSh rat: assessment of longevity and prevalence of neoplastic and nonneoplastic diseases in necropsied rats

Median life span, 906 days, was identical for conventionally reared, ad libitum fed AXC/SSh male and female rats and exceeded that of most other conventionally or barrier maintained rats. AXC/SSh rat longevity partially reflects the 25% incidence of moderate to severe nephropathy occurring at 30 to 41 months. Because male survival was related to sibship, p less than .02, and female survival was not, p greater than .05, a genetic component may affect male longevity. Maximum body weight was achieved during the initial 20% of life span and maintained through the final 10% when mean loss was 14 and 15%, respectively, for males and females. Pituitary adenomas occurred in 65% of females and 10% of males. Mammary adenocarcinoma occurred in 26% of females. Interstitial cell tumors were not detected in males younger than 24 months. Prostate adenocarcinomas occurred in 23% of males older than 29 months. The longevity of AXC/SSh rats and their low incidence of nephropathy suggests they are an attractive model for studies in aging.