Potassium-Channel Activation in Response to Low Doses of γ-Irradiation Involves Reactive Oxygen Intermediates in Nonexcitatory Cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 90; no. 3; pp. 908 - 912
• Main Authors: KUO, S. S, SAAD, A. H, KOONG, A. C, HAHN, G. M, GIACCIA, A. J
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.02.1993; National Acad Sciences
• Subjects: Acetylcysteine - pharmacology; activation; Animals; Biological and medical sciences; Biological effects of radiation; Cell Line; Cell lines; Cell membranes; Cells; channels; Dose response relationship; Dose-Response Relationship, Radiation; Electric Conductivity; Electric current; Electric potential; Free Radical Scavengers; Free Radicals; Fundamental and applied biological sciences. Psychology; gamma -radiation; Gamma Rays; Hydrogen Peroxide - pharmacology; Ionizing radiation; Ionizing radiations; man; Microelectrodes; Oxidases; Oxygen - metabolism; potassium; Potassium - metabolism; Potassium Channels - drug effects; Potassium Channels - metabolism; Potassium Channels - radiation effects; Protein Kinase C - metabolism; Radiation dosage; Tissues, organs and organisms biophysics; Human; Signal transduction; Ionizing radiation; Regulation(control); Gamma radiation; Lung; Second messenger; Patch clamp method; Ionic channel; Potassium; Mechanism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.90.3.908

Active oxygen species are generated during pathophysiologic conditions such as inflammation and ionizing radiation exposure. We tested the hypothesis that an early cellular event in response to these species involves regulation of ion channels. We exposed cells to γ-irradiation or treated them with hydrogen peroxide, xanthine/xanthine oxidase, or [3H]thymidine and then monitored channel activity by the technique of whole-cell voltage clamping. Recordings showed that both normal and tumor cells exhibit an increase in K+currents after treatment with radiation, H2O2, and xanthine/xanthine oxidase but not with high specific activity [3H]thymidine, suggesting that the signal for K+channel activation originates at the cell membrane. A single noncytotoxic dose of 10 cGy induced measurable levels of K+currents, suggesting that the induction of currents regulates biochemical changes in response to stress. To test whether channel activity is sensitive to active oxygen species, we pretreated cells with N-acetyl-L-cysteine (NAC) to increase cellular pools of free radical scavengers before radiation. In NAC-pretreated cells, K+channel activation by γ-irradiation was abolished. It has previously been shown that protein kinase C (PKC) is activated by ionizing radiation and can regulate K+channels in some cells. However, the effect of radiation on induction of K+channel activity was independent of PKC, since cells chronically exposed to phorbol esters still produced K+currents after radiation. These results suggest that an early cellular response to oxidative stress is the activation of K+channels.