Quantitative morphological studies of aging changes in the kidney of the Lewis rat.

Spontaneous aging changes in the kidneys of the rat have been previously described. In the Lewis strain, we performed semiquantitative studies of kidney histology and quantitative studies of glomerular basement membrane thickness and mesangial area in animals aged 6-30 months. There is a progressive increase in glomerular basement membrane thickness and mesangial area throughout the life of the rat. Spontaneous glomerulosclerosis in the Lewis rat does not appear to be as extensive as in other strains. The importance of spontaneous glomerulosclerosis in studies of induced kidney disease is emphasized.