[Late radiation effects in the microcirculation system of the mouse brain after chronic low-dose irradiation]

The radiation reaction of the mouse brain microvascular system was investigated 15 months after chronic (dose-rate was 3 cGy/day) and acute (dose-rate 3.2 Gy/min) gamma-irradiation. Late pathological changes in the microvascular system after the acute irradiation (3 Gy) were not found. In the same time, after chronic irradiation with equivalent dose (the accumulated dose was 3 Gy) the depletion of endothelial cell population, and multiple foci of minor pathological changes of endotheliocyte ultrastructure at as many as 50% of the population were revealed. It may be more likely to lead to reduction of tolerance of brain microvascular system to an acute radiation (10 Gy) in the late period after chronic exposure. The mechanism of impairment of brain microcirculation after low chronic irradiation will have to understand.