[Histochemical and ultrastructural studies on the anti-edema and radiation-protective effects of 0-(beta-hydroxyethyl)-rutosides in the rat brain after single-dose irradiation. 1. Electron microscopy study of terminal blood circulation].

The changes in the terminal blood stream appeared with and without protection by 0-(beta-hydroxyethyl)-rutoside (HR) were studied in irradiated rat brains by means of the electron and light microscope. Thirty minutes before irradiating the animals with doses of 1, 5, 10, and 20 Gy, they were given simultaneous i.p. and s.c. doses of 250 mg each of HR per kg of body weight or, as a control, of physiologic NaCl solution. 2, 6, 9, and 14 days after the irradiation, small tissue specimens from the parasagittal parietal cortex were examined according to the following criteria: 1. number of widely open, i.e. well perfused capillaries and small vessels, 2. number and size of perivascular, optically unstructured "light haloes" which are signs of intracellular oedemas of the perivascular astrocyte processes, 3. incidence of hyperchromic, partly shrunken neurons. The control animals not pretreated with HR showed a collapse of most capillaries and an increase in number and size of "light haloes" around capillaries, arterioles and venules. In the electron microscope, these haloes corresponded to the strongly swollen parts of the perivascular neuropile consisting mainly of oedematous astrocyte processes. These severe perivascular cell alterations were prevented for all dose ranges by the pretreatment with HR. Thus our findings do not only demonstrate a clear antiedematous effect of HR on the radiogenic cell oedema of the perivascular neuropile, they support moreover the working hypotheses with regard to the mode of action of this substance as a "membrane protector".