Effect of a Supralethal Dose of Radiation on the Blood-Brain Barrier
ARMED FORCES RADIOBIOLOGY RESEARCH INST BETHESDA MD
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Sprague-Dawley rats were subjected to a whole-body dose of 15 krads of mixed gamma-neutron radiation. Following irradiation, the animals were intravenously injected with horseradish peroxidase HRP and sacrificed. The medullae of these animals were fixed either by perfusion or by immersion, incubated in a substrate medium and processed for electron microscopic examination. In control animals subjected to the same procedures, the reaction product of the enzyme HRP and its substrate was confined to the lumina of the blood vessels in the brain fixed by immersion and completely washed out of the blood vessels of the brain fixed by perfusion. The brain tissue of the irradiated animals injected with HRP and fixed by immersion exhibited a dense reaction product in the lumina of the blood vessels, in invaginations of the luminal surface, and in micropinocytotic vesicles of the endothelial cell cytoplasm. The most significant alteration in the medullary tissue of the irradiated animals was an increase in the number of micropinocytotic vesicles in the endothelial cells. It appears, then, that damage caused by high doses of radiation initiates increased vascular permeability which may lead to the edematous condition observed in the irradiated animal.