Carcinogenicity of endrin.

Endrin is carcinogenic for rats, and most likely also for mice and dogs. Endrin caused significant incidences of malignant neoplasms at all sites. In one study, female rats were susceptible to the development of neoplasms of the endocrine organs, particularly carcinomas of the adrenal and pituitary glands as well as neoplasms of the reproductive system. In other studies, female rats tended to have carcinomas of the endocrine system, the mammary gland and reproductive system, and male and female rats lymphomas. Rats developed unusual malignant neoplasms, such as Kupffer cell sarcomas of the liver and sarcomas of the mammary gland, uterus, and stomach. There also were toxic changes, particularly in male rats, ingesting endrin. These lesions included interstitial fibrosis of the kidney; polyarteritis of the mesenteric, pancreatic and other arteries; and atrophy of the testes. Such lesions generally interfere with the health of the rats and with the development of neoplasms. Dog receiving endrin for two years had bone marrow hyperplasia, lesions of the thyroid gland and lesions of the skeletal muscle, and hyperplasias or neoplasms of other organs. One female dog had an early carcinoma of the thyroid gland. Mice ingesting endrin developed increased incidences of carcinomas of the liver and sarcomas of the uterus.