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Induction of renal pelvic carcinoma by phenacetin in hydronephrosis-bearing rats of the SD/cShi strain.

Carcinogenicity of phenacetin (PH) to the urinary tract was tested with the use of spontaneously hydronephrosis-bearing rats. In Experiment 1, 55 SD/cShi male rats were fed with 2% PH-containing diet for 85 weeks, and 32 SD/cShi male rats fed basal diet for 85 weeks served as controls. Forty-three of 53 rats fed with PH had renal pelvic carcinoma with lung metastases in three. The mean induction time was 78 weeks. Ureteral carcinoma and urinary bladder carcinoma were observed in 2 and 6 of 53 rats given PH, respectively. No urinary tract carcinoma was found in control animals. In Experiment 2, early lesions of the kidney affected by PH were also evaluated with the use of SD/cShi and Sprague-Dawley (SD) rats. Two groups of animals containing 6 SD/cShi or 6 SD male rats per group were fed 2% PH-containing diet for 8 weeks. Control animals containing 6 SD/cShi rats or 6 SD rats were fed basal diet for 8 weeks. Simple hyperplasia was found in 5 of 6 SD/cShi rats given PH and 2 of 6 SD/cShi control rats. Papillary necrosis was seen in 4 of 6 SD/cShi and 2 of 6 SD rats given PH. SD/cShi rats, especially those treated with PH, showed higher but not significant 5-bromo-2'-deoxyuridine labeling indices in the covering epithelium of the renal pelvis and papillae. In this short term experiment PH and its metabolites, N-hydroxyphenacetin and N-acetyl-p-aminophenol, were measured in urine and plasma by using high performance liquid chromatography. Significantly higher PH and slightly higher metabolites were detected in urine and plasma of SD/cShi rats compared to SD rats. These results indicated that the renal pelvis of SD/cShi rats had more sensitivity to PH carcinogenicity. This paper provides experimental proof of PH carcinogenicity toward the renal pelvis in an animal model.