[Effect of 5-fluorouracil and irradiation of the cell kinetics of Walker carcinoma and the small intestine in rats].

A therapeutic schedule of synchronizing cytostatical-radiological treatment often used in human medicine is applied to rats carrying a Walker tumor. The effect of this treatment on the kinetics of tumor cells and epithelium of small intestine is investigated. 1. 5-Fluorouracil, i.p. during 18 and 12 hours, brings about no changes in the mitotic index; however, in the curve of marked mitoses a small fraction of cells is represented which is considered to be a consequence of the synchronization of a very small portion of tumor cells. 2. If ten hours after 5-FU-injection the cells are irradiated with a single dose of 300 rd, there occurs a distinct G2-block and a lengthening of the S-phase. These changes are found both in the 5-FU ground and in the controls. 3. 5-FU-injection thrice alternated with irradiation likewise causes a G2-block. After solution of the block a delayed increase of mitoses in the controls is going on which cannot be detected in the 5-FU group. These findings are interpreted as an effect of 5-FU on the proliferation rate of tumor tissues.