Chronic toxicity, oncogenic potential, and reproductive toxicity of p-nitroaniline in rats

Dose levels for these studies were selected mainly on the basis of subchronic studies, although consideration was also given to workplace exposure levels and proposed mechanism of tumor formation with structurally similar compounds. For the chronic study, groups of 60 male and 60 female Sprague-Dawley CD (Registered Trademark of Charles River Breeding Laboratories, Portage, MI) rats were given 0, 0.25, 1.5, or 9.0 mg/kg/day paranitroaniline (PNA) by gavage in corn oil for a period of 2 years. Parameters monitored included clinical observations, ophthalmoscopic exams, body weights, food consumption, hematology, clinical chemistry, and urinalysis at regular intervals throughout the study. All gross lesions and over 40 tissues were examined histologically for all control and high-dosage-level animals. Gross lesions, spleens, and livers of low- and mid-dosage groups were also examined histologically. For the reproduction study, groups of 15 male and 30 female rats, designated as F0 generation, were given PNA at the same levels as the chronic study for 14 weeks prior to mating and during mating, gestation, and lactation. Selected groups of 15 male and 30 female rats of the F1 generation received the same dose of PNA for 18 weeks prior to mating and during mating, gestation, and lactation. F2 pups were observed through weaning at which time they were euthanized. Observations made during the study included body weights, food consumption, mating and fertility indices, pup and litter survival indices, and histopathology of selected tissues. In the chronic study, except for a slight decrease in survival of high-dose male rats late in the study, survival in all treated groups was comparable to controls. Blood methemoglobin levels were elevated in the mid- and high-dosage groups, while slight anemia was observed in the high-dosage group also. Spleen weights were significantly increased in the high-dosage groups. An accumulation of brown pigment was observed in the cytoplasm of the sinusoidal macrophages or littoral cells of the liver and in the reticuloendothelial cells of the spleen. No treatment-related increase in tumor incidence was observed. In the reproduction study, no consistent pattern of effect from treatment between the F0 and F1 generation was seen in mating, pregnancy, or fertility indices. Thus, administration of PNA at levels which produced significant methemoglobinemia and low-level anemia in the rat and histological changes in the spleen produced no tumors or reproducible effects on reproductive performance.