Bioassay of p-phenylenediamine dihydrochloride for possible carcinogenicity.

A bioassay of p-phenylenediamine dihydrochloride for possible carcinogenicity was conducted using Fischer 344 rats and B6C3F1 mice. p-Phenylenediamine dihydrochloride was administered in the feed, at either of two concentrations, to groups of 50 male and 50 female animals of each species. The high and low concentrations of p-phenylenediamine dihydrochloride were, respectively, 1,250 and 625 ppm for both rats and mice. After a 103-week period of compound administration, there were additional observation periods of 2 weeks for rats and 1 week for mice. Twenty animals of each sex and species were placed on test as controls. There were no significant positive associations between the concentrations of p-phenylenediamine dihydrochloride administered and mortality in rats or mice of either sex. Adequate numbers of animals in all groups survived sufficiently long to be at risk from late developing tumors. Slight dose-related mean body weight depression was observed in female rats and the mean body weights among high dose male rats and dosed female mice were slightly depressed in relation to their respective controls, indicating that the concentrations of p-phenylenediamine dihydrochloride administered to these animals in this bioassay may have approximated the maximum tolerated concentrations. Since no distinct mean body weight depression relative to controls, no significant accelerated mortality, and no other signs of toxicity were associated with administration of p-phenylenediamine dihydrochloride to male mice, it is possible that these animals may have been able to tolerate a higher dietary concentration. None of the statistical tests for any site in rats or mice of either sex, including time to leukemia or malignant lymphoma analysis in female mice, indicated a significant positive association between compound administration and tumor incidence. Under the conditions of this bioassay, there was no convincing evidence that dietary administration of p-phenylenediamine dihydrochloride was carcinogenic in Fischer 344 rats or B6C3F1 mice.