Pathological changes during aging in barrier reared fischer 344 male rats

Abstract

Pathology, microbiology, and selected serum chemistries were evaluated in 144 male Fischer rates from 4 to 33 mo of age. The rats were reared and maintained under barrier conditions, which successfully excluded the introduction of major infectious disease agents throughout the entire study, including Mycoplasma pulmonis. A wide variety of pathology was found and tabulated, and many lesions were found to increase in severity and incidence with age. Involution of the reproductive system, myocardial degeneration and fibrosis, chronic renal disease, sclerosing bile ductal hyperplasia, and chronic passive splenic congestion were the most frequent nonneoplastic lesions. Testicular interstitial cell tumors, mononuclear cell leukemias, and pituitary adenomas were the most frequent tumors, with a large number of other types occurring in low incidence. There was a high correlation of renal disease severity with increasing age. Serum total protein and albumin decreased with age, while alpha-1 globulin and cholesterol increased. No changes were seen in serum sodium, potassium, urea, creatinine, or other protein components.