Long-term feeding study of N,N'-diphenyl-p-phenylenediamine in F344 rats

Groups of 50 F344 rats of each sex were fed a diet containing 0.5 or 2% of N,N'-diphenyl-p-phenylenediamine (DPPD) for 104 weeks and were killed 8 weeks after the cessation of DPPD administration. DPPD-treated rats of both sexes showed a dose-dependent reduction in body weight gain, but no lower survival rate, when compared with untreated control rats. Blood and urine analysis showed no remarkable changes due to the treatment. Calcium deposition in the kidney of males was the only significant histological change relating to the treatment. Tumors were found in many organs of all groups, but a significant increase of tumor induction in DPPD-treated groups was not observed.