The Effect of Low-Dose Irradiation on Proliferation of Mammalian Cells In Vitro

The effect of low doses of gamma radiation on proliferation of Raji lymphoma cells and Chinese hamster fibroblasts in vitro has been investigated. It is shown that irradiation in the dose range between 2 and 20 cGy (maximum at 10 cGy) stimulates growth of cultured cells due to the shortening of the lag phase of cell growth, with the duration of the doubling time being unchanged. Preirradiation of growth medium in this dose range also stimulates cell proliferation, though to a lesser extent than irradiation of cells and the medium does. The stimulatory effect manifests itself in an increase in the cell number as well as in the size and number of colonies.