Kidney and liver tumors in rats from 4,4'-methylene bis (2-carbomethoxyaniline)

4,4'-Methylene bis (2-carbomethoxyaniline), also known as methylene-bis methyl anthranilate (MBMA), was added to the diet of male and female ChR-CD rats for up to two years at levels of 0, 1500, and 15,000 ppm. Fifty rats of each sex were used at each dietary level. Female rats at both dietary levels of MBMA had a lower body weight gain and lower food efficiency values than did the controls. High-level males and females showed a slight anemia; all other clinical laboratory tests were within normal limits. MBMA caused slight degenerative histologic changes in the liver and kidney of both sexes at both dietary levels. High-level males developed a statistically significant increase in kidney and liver tumors when compared to controls (p less than 0.05, Fisher's Exact Test, one tail). High-level females had an elevated kidney tumor incidence compared with controls (p less than 0.10). There was a statistically significant lower incidence in pituitary tumors in high-level males (p less than 0.05) and in high-level females (p less than 0.10) than in controls. High-level females had a lower incidence of mammary tumors (p less than 0.05) compared to controls. MBMA was considered to be a carcinogen of moderate potency in rats, since tumors were not found until 18 months on test using a comparative large dose (1.5% of diet).