In the control group of old untreated male rats, all animals exhibited progressive age-related nephropathy, including regenerative hyperplasia of tubular epithelial cells and formation of protein casts (Figure 8). Additionally, aging was associated with increased lymphoplasmacytic infiltration in the interstitium of the kidneys. No histopathological signs of tubular epithelial vacuolization were detected in any of the animals in this group.