[Effect of polypeptide factors of the thymus and epiphysis on radiation carcinogenesis].

Three-month-old female rats were exposed to a single x-ray irradiation (400 rad). Beginning from week 3 after irradiation the animals were treated with 0.2 mg of thymic factor (thymarin) or pineal factor (epithalamine) dissolved in 0.2 ml of normal saline. Meanwhile the control rats were given the same amount of the solvent. The treatment was carried out for 10 days monthly during the lifespan. Application of epithalamine reduced the incidence of all the tumors and that of malignant tumors 1.3- and 2.7-fold, respectively. The preparation suppressed the development of mammary adenocarcinomas, tumors of the thyroid gland, leukemias, and malignant tumors of the uterus. Administration of thymarine decreased the incidence of malignant tumors (1.9-fold) mainly that of mammary adenocarcinomas. It is suggested that normalization of hormonal and metabolic shifts and related immunity disorders that develop as a result of exposure to ionizing radiation prevents the development of tumorous process more effectively than application of specific immunity stimulants.