[Use of lymphocytic DNA by the urothelium of bladder tumors]

In 35 rats tumors of the urinary bladder were induced by nitrosomethylurea. A rubber loop was established on the neck of the urinary bladder and tightened for 1.5 h. This allowed one to completely isolate the tumor from the circulation. Shortly after the tightening of the loop 3H-thymidine was injected intraperitoneally. The rats were sacrificed at different times after the loop was removed. The tumors were examined by histoautoradiography. Lymphocytes were the first labeled cells that appeared in the stroma of the tumors 9 h after operation. Following 36 hours the radioisotope was detectable in the epitheliocytes. That meant that the label was reutilized by the tumor urothelium. It was shown that the only donor of the isotope could be a live labeled lymphocyte transmitting its own DNA in the course of a direct contact with the tumor cell. That was a manifestation of the trophic function of lymphocytes. It is concluded that lymphocytes support the proliferative activity of the tumorous tissue.