Promoting effect of peroxisome proliferators in two-stage rat renal tumorigenesis.

A two-stage rat renal tumorigenesis model was employed to examine the promoting effects of peroxisome proliferators in the kidney. Groups of 20 male F344 rats were given 0.05% N-ethyl-N-hydroxyethylnitrosamine (EHEN) orally for the first 2 weeks as the initiator. Subsequently they were treated with clofibrate, simfibrate or di(2-ethylhexyl)phthalate (DEHP), respectively, at dietary concentrations of 0.35%, 0.35% and 1.2% for 24 weeks and killed for microscopical examination of the kidney. The incidences of renal cell tumors (RCT) and the numbers of RCT/kidney in rats given DEHP after initiation were significantly increased as compared to the controls. On the other hand, renal promoting effects were not evident in groups given clofibrate or simfibrate. Under the condition of this study, DEHP was found to act as a renal promoter.