Effect of Roentgen Irradiation upon Lymphatic Flow in Rats

Abstract

The reactions of tissue to roentgen rays and radium have been studied and described for years. Throughout this time, however, little has been learned concerning the reactions of lymph channels and the flow of lymph to these forms of radiant energy. This may be attributed, as Ewing (1) pointed out, to the difficulty with which changes in lymphatics are followed experimentally. The purpose of the present communication is to report observations on the effect of roentgen irradiation upon lymphatic flow in rats. The use of thorium dioxide as a contrast medium for roentgen visualization of lymphatics in animals has been described by Menville and Ané (4), and Pomeranz (5). The ease with which colloidal thorium is absorbed by the lymphatics and concentrated in neighboring lymph nodes, where it may be demonstrated roentgenographically, suggested to us its use for studying the adequacy of lymphatic flow following roentgen therapy. Under normal circumstances 0.05 c.c. of thorium dioxide injected subcutaneously into the hind foot of a rat may almost invariably be seen radiographically in the region of the popliteal or inguinal node within an hour following the injection. If both hind feet are injected simultaneously, the appearance time in the respective lymph nodes is about the same. It seemed reasonable, therefore, to attempt testing the competency of lymphatic flow following irradiation by irradiating one leg and using the contralateral extremity as a control. If the popliteal or inguinal nodes failed to appear on the irradiated side. one might assume that lymphatic flow had been interfered with by the irradiation. If, however, thorotrast could be demonstrated in the nodes on both sides it would seem that irradiation, under the particular conditions, had not influenced the flow of lymph. White rats were used throughout the experiment. Intraperitoneal nembutal anesthesia was used as a sedative during the treatment, and nembutal or ether while the animals were being radiographed. One hind leg of each animal was irradiated, the contralateral leg being used as a control. Care was taken to alternate between the right and left legs, so that one-half of the series of rats were treated over the right leg, and the remaining half over the left leg. The animal was protected with lead sheeting, the only region exposed being a small area over the leg between the ankle and the thigh, measuring about 1 cm. square. Two series of experiments were undertaken, one with rays generated at 135 kv., the other at 200 kv. The first experimental group included 21 rats. The physical factors employed were as follows: 1:36 kv., 4 ma., 0.25 mm. Cu plus 1 mm. Al filtration, 30 cm. TSD. The total dose delivered to the skin3 was 2250 r (in air) given at one time in about forty minutes. This produced epilation and a moderately severe skin reaction in the treated area within two weeks after exposure, which healed readily.