Renal cysts and associated renal tumours in male ddY mice injected with ferric nitrilotriacetate.

In experiments using ferric nitrilotriacetate (Fe-NTA) as a renal carcinogen, multiple renal cysts are often observed in addition to renal tumours. In the present study, we used 3-week-old male ddY mice and examined the relation between renal cysts and cancer development. Four months after the start of Fe-NTA administration, we observed cysts in the renal cortex in all Fe-NTA-treated mice, but not in Fe-free NTA-treated mice. Three types of cysts were observed, but only those which originated from the renal proximal tubules showed multilayered or papillary growth of cyst epithelial cells. Using histochemical staining, we found a cyst formation-tumour induction sequence, and the supposed cystic-papillary tumour induced by Fe-NTA was of proximal tubular cell origin. We also found that the minimum dose of Fe-NTA capable of inducing renal tumours in ddY mice was 10 mg of iron/kg/day, four times in 2 weeks.