| Abstract: | Skin tumors induced by the subcutaneous injection of 3-methylcholanthrene (3-MC) in New Zealand Black (NZB) mice had a delayed development and lower frequency compared with BALB/c and C57BL mice. In the SJL/J strain, the incidence of tumors was lower than in the NZB, but with the same delayed development. Most of the tumors in the BALB/c, C57BL, and SJL/J strains were sarcomas; more than one third of the tumors in the NZB mice were squamous cell carcinomas. The greatest frequency and most rapid development of tumors in the NZB, as a function of age at the time of injection of 3-MC, occurred at 4 months. Young (3.5 and 7 weeks) and 12-month-old tumor incidence in the 4-month-old NZB was decreased by treatment with antithymocyte serum (ATS). Five hundred rad whole-body x-irradiation accelerated the onset of tumors but did not increase the final incidence. 3-MC injection and the presence of skin tumors had no influence on the development of glomerulonephritis or hematopoietic neoplasms in the NZB mice. Coombs' positive anemia was not influenced by 3-MC injection, but there was an earlier and increased incidence of positive Coombs' tests in tumor-bearing animals. Liver aryl hydrocarbon hydroxylase (AHH) specific activity was low in the young NZB, increased gradually with age, and was higher in the female mice. |
