Pathological lesions in the spontaneously diabetic BB Wistar rat: a comprehensive autopsy study

A total of 145 BB Wistar diabetic rats, 46 of their nondiabetic siblings, and 43 outbred Wistar rats were autopsied and the frequency of lesions in all organ systems were determined. Common strain-related lesions included pulmonary infections, granulomas, lymphoid hyperplasia, lymphomas, lymphocytopenia, eosinophilia, supradiaphragmatic accessory lobes of the liver, and prostatic atrophy. These suggest some basic strain-related abnormalities of the immune system that were selected by the process of inbreeding. Diabetes-related lesions were insulitis, testicular atrophy, cataracts, hepatic fatty change, pancreatitis, lymphocytic thyroiditis, hypoglycemic brain damage, central pontine myelinolysis, stomach erosions, and idiopathic megacolon. Many of these are sequelae of human juvenile-onset diabetes and support the validity of the BB Wistar rat as an animal model for human diabetes mellitus. The absence of several important sequelae of the human disease (i.e., diabetic nephropathy, atherosclerosis, and severe microangiopathy) suggests a degree of infidelity as a model for human diabetes mellitus. Nonspecific lesions occurring in all three groups of rats included myocardial degeneration and fibrosis, splenic extramedullary hematopoiesis, and chronic progressive glomerulonephropathy.