Characterization of age-associated kidney disease in Wistar rats

Kidney disease was studied patho-histologically, electron microscopically and immunologically in Wistar rats ranging in age from 2 weeks to 24 months. Glomerular lesions characterized by adhesion of podocyte foot processes were first detected at 3 months of age. The kidney lesions became more pronounced with age, as manifested by an increase of mesangial matrix, basement membrane thickening, crescent formation and hyalinization of glomeruli, and tubular degeneration. Evidence for the deposition of immune complexes in the kidney was obtained by immunofluorescence and electron microscopy, as well as by immuno-electrophoretic analysis of kidney elutions. Tests with antiserum reagent against Moloney leukemia virus antigen revealed its presence in some but not all glomeruli. The presence of other viruses in Moloney leukemia virus negative glomeruli was not ruled out. Serum autoantibody against an array of rat tissues could not be detected. Therefore, it would appear that autoimmune mechanism may not be the primary underlying cause of pathogenesis of the disease. Accordingly, the disease could be referred to as chronic immune complex glomerulonephropathy with nephrotic syndrome, but sources of the antigens in the complex were mostly unknown, althougn virus could be one portion of them. The possibility that diet antigens may also be present in the complex seems unlikely because attempts to demonstrate serum antibodies against diet pellet in old rats were unsuccessful.