[Age-related non-tumorous lesions in SPF C57BL/6 mice with special reference to amyloidosis]

Non-tumorous pathological changes in C57BL/6 CrSlc mice, which were reared under a barrier system and died spontaneously, were examined. At 3 months intervals 125 to 209 mice were purchased at 4 weeks of age and raised for the supply of aged animals. A large portion of the mice were used for various experiments between 3 and 30 months of age, while not a small number died spontaneously and were autopsied. The major non-neoplastic lesion was amyloidosis, with incidence of 55.5% and 74.4% for the autopsied female and male, respectively. The organs involved were the liver, kidneys, spleen, adrenal glands, ileum, heart and lungs. Skin ulceration and its scar, cerebral vascular calcification, glomerulosclerosis and sepsis in both sexes, distension of the seminal vesicles in males, fibroblast growth of the adrenal glands in females were commonly found. Incidence of spontaneous neoplastic lesions was 69.7% and 55.1% for the female and male, respectively.