Substrate-enzyme characteristics after derangements of biological combustion processes. Estimations of organism's long term exposure to uranium ore dust

Under uranium-mining and processing conditions industrial dust of uranium ore (IDO) is key anthropogenic factor of effect on organism. Industrial dust of uranium ore contains trace of 238uranium oxide making effects of low and ultralow radiation doses along with silicon derivatives, salts of heavy metals and other contaminants. In recent years epidemiological studies showed that along with commonly encountered radiation- induced pathology in zones with radiation problems general somatic morbidity with symptoms of chronic disease with protracted course essentially increased. Above-mentioned facts indicate the exigency of systematized study the nature of systemic effect of ionizing radiation on organism at low doses. Structural and functional irregularities, metabolic imbalances and dyscrasia induced by irradiation can become indicators in this direction. Biological combustion processes performing complex of reductive and oxidative conversions directed to energy-rich compound synthesis occupy a special place among highly sensitive and informative homeostasis systems. In order to reveal the nature of ionizing radiation effect on organism at low doses and search for a relation 'Dose - Effect' we carried out series experiments with different doses of industrial dust of uranium ore from Stepnogorsk mining and chemical complex. Dose load calculation was carried out with a glance for threshold limit value (TLV) of dust control in work zone. Three dose loads satisfied to 5, 10, and 50 times to TLV were studied. Total time on inhalation primer makes up 120 days at doses equal to 5 and 10 times TLV and 60 days at dose 50 times TLV Value of total accumulated dose in the first two series varies within 11 and 22 micro Sv per 120 days of inhalation and is 55 micro Sv per 60 days in the third series. Substrate - enzyme relationships of three energy systems: terminal stages of glycolysis, intermediates and enzymes from Krebs cycle, as well as certain products from lipid peroxidation/ antioxidant defense were studied. Stages of glycolysis were monitored via enzymatic measuring the activity ratio between oxidized and reduced forms of lactate dehydrogenase as well as a concentration of lactate and pyruvate. Dynamics of Krebs cycle was assessed via variations in isocitric acid and malate content as well as activity of four dehydrogenases in citric acid cycle. Derangements in lipid peroxidation/ antioxidant defense were appraised via dynamics of malonic dialdehyde and superoxide dismutase activity. Preliminary analysis of obtained results showed in cytosol the vast majority of rat viscera concentration figures of analyzed metabolites change in different ways. At ultralow dose exposure adaptive increase of certain metabolites synthesis were detected and duration of such response was maximal. With increasing the duration of uranium dust exposure this pattern is gone. In organs of excretory system the opposite trend in quantitative figures found out in earlier terms of inhalation priming. Possible mechanisms of observed changes are discussed.