Alterations in the rat kidney associated with sodium saccharin feeding

Sodium saccharin has previously been demonstrated to induce hyperplasia and tumors of the urothelium of the rat urinary bladder. It was fed as 5% of the diet to male F344 rats for 2 years. In the present experiment, mild simple hyperplasia of the urinary bladder epithelium was again frequently observed, and a marked nodular and papillary hyperplasia of the urothelium of the kidney pelvis was also found in approximately half of the sodium saccharin-fed rats. This was infrequently associated with focal calcification of the renal papilla and pelvis. In contrast, rats fed sodium saccharin had a significantly reduced incidence of the interstitial nephritis frequently observed in older rats. No significant incidence was observed of lesions of tissues other than those of the urinary tract.