Radiation-Induced Efflux of Intracellular Potassium

Irradiation of the isolated frog sciatic nerve previously equilibrated in a solution containing⁴² K with doses of 10 to 20 krads at a dose rate of 15 krads/min causes an increased efflux of⁴² K associated with the period of irradiation. This result, together with previously published findings, demonstrates that irradiation at a sufficiently high dose rate causes an increased permeability of the axonal membrane and a net loss of potassium ions. Analogous experiments with cultured tumor cells showed that in this case there is no net loss of potassium after doses up to 230 krads at 65 krads/min, but there is a much greater rate of exchange of intra- and extracellular potassium ions without any obvious damage to the cell membrane in the first 6 hours after irradiation.