Sova O. Kinetics of 131І in the organism of laboratory rats, dose formation and biological effects of irradiation at internal intake

Dissertation is devoted to study of 131I income, storage and outcome patterns and features income, storage and excretion patterns and features in laboratory rats organs and tissues, formation of absorbed doses for single and two modes prolonged oral intake; doserelated hematologic and cytogenetic changes were identified. After a single income, the isotopes retention is described by two exhibitors with short and long effective half-life. It also was revealed, that the second content radioiodine tissue in the body is skin, which acts as a isotopes reserve depot. Methodology that allows to estimate dose on blood corpuscles (BC) for macrodosimetric indicators was developed and used for practical calculations. Method of calculating doses of radionuclides contained in the thyroid gland (TG) and skin additional irradiation was developed and applied. It was established, that thymus suffers the most of exposure. A dose-dependent increase of effective half-life of isotope (Тef) in TG until dose achieves ~ 34 Gy was found, which can be explained by the development of hypothyroidism caused by radiation of thyroid tissues. For doses more than 34 Gy Tef begins to decline, apparently in connection with the collapse of thyroid tissue. Also, it was found that a single partial blocking thyroid has virtually no radioprotective effect: absorbed and effective dose in TG is not reduces, only dose rate does. For long-term income of 131I to body of rats, the accumulation in TG is determined by three interrelated dose-dependent variables - effective half-life, iodine in thyriod deposition factor and thyroid weight. Method of quantitative determination of these indicators was developed and applied. After long-term income of 131I to body of rats, the number of small lymphocytes in the bloodstream significantly decreased, compared with control, apparently caused by gamma-irradiation of thymus with iodine deposited in the TG. The frequency of aberrant metaphases significantly increased by chromosomal type rearrangements, namely dicentrics with paired fragments, free acentric fragments and abnormal monocentrics, whose appearance is considered as a specific response to the ionizing radiation. There was a probable increase in genomic aberrations.