Acute tissue injury and subsequent inflammation, including tissue edema and erythema, can be caused by sufficiently high levels of exposure to gamma radiation. The mechanism of this tissue injury is related to the generation of reactive oxygen intermediates (ROI) which chemically alter biological molecules and cell physiology. Cell membrane lipids are vulnerable to ROI-mediated lipid peroxidation that then leads to many of the acute tissue effects. We hypothesize that increased cell membrane permeability leading to osmotic swelling and vascular transudation is one of these effects. Thus we used adult postmitotic rhabdomyocytes in culture and microscopic fluorescence techniques to quantify radiation-induced changes in cell membrane permeability. Based on time-resolved dye flux measurements, a characteristic lag time of 34 +/- 3 min was determined between exposure to 160 Gy of gamma radiation and the decrease in membrane permeability. Administration of 0.1 mM nonionic surfactant Poloxamer 188 added to the cell medium after irradiation completely inhibited the dye loss over the time course of 2 h. Thus a reproducible model was developed for studying the mechanism of acute radiation injury and the efficacy of membrane-sealing agents. As only supportive measures now exist for treating the acute, nonlethal injuries from high-dose radiation exposure, agents that can restore cell membrane function after radiation damage may offer an important tool for therapy.