Acta Facultatis Ecologiae - Technická univerzita vo Zvolene

35DISCUSSIONThe ionising radiation exerts profound effectson the mucous lining of the gastrointestinal tract: asa result of its impact on the dividing enterocytes inthe crypts the continuous replacement of the dyingand desquamating cells on the top of the enteric villiis interrupted. This state leads to the interruptionof the regeneration processes of the gut mucousand to the loss of its functions. Clinically, this statemanifests in diarrhea and in a subsequent cachexia.The damage of the barrier functions of the intestinalmucous caused by the high radiosensitivityof the enterocytes, along with the disruption of theimpermeability of blood capillaries conditioned bythe high radiosensitivity of endothelial cells belongto the typical symptoms of the radiation disease[10]. The increased permeability of blood capillariesleads to development of hemorrhagic diatesisas it was observed in our experiments on the eyesof the irradiated rats and on the presence of bloodydiarrhea.Microorganisms commonly present in the gastrointestinaltract penetrate after irradiation throughthe intestinal mucus and the damaged capillaries ofthe intestinal wall into the blood circulation, wherethey acts as antigens. In irradiated organisms,however, because of lymphopenia and monocytopeniacaused by radiation the immunoligicalresponse is strongly suppressed. This can lead tofurther reproduction of bacteria and to the developmentof bacteremia and of subsequent toxinemia.The prolonged depression of immunological reactionsas a result of radiation leucopenia leads tosepsis, followed by death of the animal.From the point of view of the early diagnosticsof the radiation disease the most important are thechanges in white blood cells. In our experiments inall irradiated individuals a statistically significantdecrease of the total number of leucocytes and anincrease of neutrophils in comparison with controlsoccurred. Shortly after irradiation leucopeniacharacterized by lymphopenia and neutrophiliawas observed. The changes in the white bloodpicture are caused not only by the damage of thebone marrow, but also of the lymphoid tissues withmyelopoetic functions, like thymus, the lymphaticnodes, and the Bursa fabricii in birds [6, 12]. Thelymphocytes, on the other hand, show a high degreeof direct radiosensitivity and their number inperipheral blood decreases as a result of their directextinction. The immunosuppressive effect of radiationcould be critical for the irradiated organism, asmuch it becomes sensitive not only to various infections,but also to the common microflora, whichleads to postradiation bacteremia [1].In the total number of erythrocytes as well asin the hemoglobin content a statistically non-significantincrease was recorded 3 days after irradiation.The increase of the hematocrit value wasin this time interval statistically significant. Startingwith the 6 th day after irradiation a statisticallysignificant increase in CPE was recorded, whichwas prolonged up to the 9 th day. The hemoglobincontent was increased still on the 6 th day after irradiation,however, on the 9 th day a marked decreaseof this parameter in comparison with controls occurred.The hematocrit values decreased only onthe 9 th day after irradiation. The following changesin the red blood picture are due to the high radiresistenceof the erythrocytes and also due to the factthat the body disposes with large reserves of theseblood cells deposited in the spleen and in liver[4, 7]. The anemia which belongs to the basic symptomsof the radiation disease manifest itself as thelatest of the hematological changes. The extent ofthe hypoplastic or aplastic anemia and the degreeof damage which are documented after irradiationdepend, except of the radiosensitivity of cells,also on the exposition dose and on the dose rate,the regeneration capacity of the cells, e.g. Subakovet al. [11] using chronical irradiation with a totaldose of 0.9 Gy of gamma-rays recorded an increaseof the number of reticulocytes in the peripheralblood, which is an evidence of an increased erythropoesisin the bone marrow. In the case of the doseapplied by us irreversible changes in the bone marrowcan be assumed, which leads to the developmentof the anemia described above. The normaltissue is replaced by the fat tissue which is unableto produce differenciated blood cells. Also the destructionof existing cells (karyorexis, karyolysis)and cytogenetic damage of cells occur (4).AcknowledgementsThe study was supported by the grant VEGANo. 1/2378/05 and by the grant No. MSM6215712402 from the Ministry of Education, Youthand Sports of the Czech Republic. The authorswish to thank for financial support of the project.