Análise da eriptose e concentração extracelular do potássio nas hemácias irradiadas com diferentes taxas de dose

Abstract

The blood irradiation can be performed with X-rays produced by an accelerator, or by a specific equipment for irradiating blood with radioactive material (Ce-137 or Co-60) in its interior that, through the radioactive decay of these elements, emits gamma rays. Blood irradiation is a very important procedure in the prevention of Transfusional Host Graft Disease (DECHT) by inactivating T lymphocytes. This disease is a rare and fatal syndrome because the transfused lymphocytes of a blood donor attack the cells of the receptor. Thus, the irradiation of cellular components (red blood cells, platelets and granulocytes) is the only way to prevent DECHT. This study consisted of using different dose rates in blood irradiation using the Gammacell 1000 blood specific irradiator, combined with a linear accelerator of 662 keV of photon energy, and 6MV of nominal energy. We evaluated how these different rates influenced the erythrocyte structures, which are responsible for the oxygen transport in our organism. The total dose of 25 Gy was administered by both irradiation methods in order to inactivate the lymphocytes by the graft versus transfusional host disease. The main goal of this project was to verify the eriptosis and the concentration of extracellular potassium of the red blood cells in the irradiated blood samples with different dose rates. The samples were stored during the validity period of the CPDA-1 bags, which is of 35 days, but after irradiation this period decerases to 28 days due to the cellular damage produced by this procedure. The methodology consisted in using 10 bags of red blood cells from voluntary donors from the Biobank of Hospital de Clínicas. Each bag of red blood cells was fractionated in three other bags with smaller volumes, totalizing 30 bags for the study. These samples were irradiated with four dose rates by the linear accelerator, by the specific irraditerator and without radiation (control samples). From each bag, 5 measurements were carried out totalizing 150 samples. The irradiations were performed with a total dose of 25 Gy in the median plane of the bags, and at different dose rates using the linear accelerator to evaluate cell damage, such as eryptosis (erythrocyte death) and extracellular potassium concentration. As a result, it was verified that the cellulaar damage inceases with the dose rate, and very close results were obtained comparing the Gammacell dose rate with the linear accelerator. Moreover, the extracellular potassium concentration increased after the use of the irradiation in the study samples, as expected. In addition, the quantity of extracellular potassium and eryptosis also increased with the dose rate.