Didenko M. N., Stezhka V. A., Zinchenko V. N.
SI «Institute for Occupational Health of NAMS of Ukraine», Kyiv
Introduction. One of the most hazardous manifestations of the general action of nanoparticles (NP) of different origin, irrespective of their sources and ways of entering the body (with air, water, food, medicines, from clothes) is their translocation into internal environment and distribution between organs, covering lungs, heart, liver, spleen, testis and brain. As regards mechanism of their penetration into the brain, two possible ways are under discussion: directly through hematoencephalic barrier or through nasal nerves.
Purpose of the work. To study peculiarities of toxicodynamic effect of NP of high disperse amorphous silica of various size on the morphofunctional status of rat brain neurocytes after a single intratracheal instillations in suspensions.
Materials and methods. The studies were conducted in 128 Vistar male rats, 190-200 body weight, divided into the control and three test groups. The morphofunctional status of deep laminars of rat’s cortex cerebri neurocytes after a single intratracheal instillation of high disperse amorphous silica nanoparticles (NP) (marks: A300 — 9 nm; A100 — 38 nm; A50 — 87 nm) under ethaminal narcosis (3,0 mg/200 g body weight), in the dose, standardized by the specific surface area (0,25 m2, providing the contact of NP with 25 % alveoli surface (series S); by the number of NP (3,0-10n/rat, Series N) and by the substance mass (25 mg/rat, Series M) were investigated. The sections of deep layers of brain large hemispheres were stained with hematoxylin-eosin and thionin by Nissle.
Results. It is established, that all NP, irrespective of their size and the tested concentrations, cause structural changes in neurocytes and separate zones of their cytoplasm, which can be presented by 3 types: а) the enhancement of neurocyte functional activity, confirmed by the partial chromatolysis of the basophilic material and marginal and perinuclear vacuolization of the cytoplasm, its partial hyperchromatolysis in preservation of the structure of the nucleus and nucleous (NP of all silica, series S, N, M); b) the inhibition, reduction or partial cessation of neurocyte functional activity, indicated by marginal or central chromatolysis of the basophilic substance of the cytoplasm with its partial lysis of nuclear chromatin or sharp cytoplasm hyperchromic staining (NP of all silica, series S, N, M); c) the dystrophic and necrobiotic changes, manifested by the total chromatolysis of the basophile substance in the cytoplasm with nucleus pyknosis in the ectopic position (in 4 months, cilica NP A100S, A300S, A100N), by perinuclear edema, occurrence of large vacuoles in the neutrocyte cytoplasm, resulting in nucleus ectopia (in 4 months, cilica NP A100M), contracted neurocytes and neurocyte-“shades”, showing irreversibility of their damage (in 1 month, NP cilica A50S, A100S, A300S, A300N; in 4 months, cilica NP A50M, A50S, A300M). The first two types (a, b) of changes of the functional state of neurocytes were followed by proliferation of neurogliac cells, which show, under their physiological part, on one side - the availability of the unfavourable chemical effect, on the other side - development of compensatory-adaptation processes in the central nervous system. The second and the third types (b, c) of structural changes in neurocytes showed the decrease in the relative number of neuroglualic cells and were found most often in rats in 1 and 4 months after the experiment, indicating the enhancement of the toxic effect of NP on the brain tissue. Conclusion. The ability of NP of high disperse amorphous cilica to penetrate through the hematoenchephalic barrier and cause a damaging effect on the brain tissue has been confirmed.
Keywords: brain neurocytes, microglia, nanoparticles (9, 38, 87 nm) of high disperse amorphous cilica, intratracheal instillation, Vistar male rats