A 2-YEAR COMPARISON STUDY OF CRL-CD BR AND HSD-SPRAGUE-DAWLEY SD RATS

In this 2-year study, the suitability of the Hsd:Sprague-Dawley SD (SD ) as a replacement for the Crl:CD BR (CD) rat was assessed by comparin g survival rates, palpable mass incidence, body weights, food consumpt ion, clinical laboratory parameters, and necropsy and histopathology o bservations. At Week 104, survival rates in the CD and SD males were 2 9 and 49%, respectively. Corresponding survival rates in females were 44 and 63%. The total numbers of animals with palpable masses and anim als with neoplasms were similar in the CD and SD rats; however, the to tal numbers of palpable masses and neoplasms were higher in the CD rat s, The incidence of corneal lesions was higher in the SD rats, whereas the incidence of lenticular opacities was higher in the CD rats, Body weights, food and water consumption. and organ weights were significa ntly lower in the SD rats. In contrast, food intake per kilogram of bo dy weight was slightly higher in the SD rats, Numerous differences in clinical laboratory parameters between the CD and SD rats were observe d. Some of these were consistent with the Increased prevalence of kidn ey disease and secondary sequelae in the SD rats, Taken together, the better survival, smaller size, and lower food consumption of the SD ra t may make it a better model fur chronic bioassays, However, the incre ased propensity for spontaneous renal disease may limit the utility of the SD rat for studying nephrotoxic compounds. (C) 1996 Society of To xicology