Problems of Radiation Medicine and Radiobiology

Oxidative phosphorylation in mitochondria of small-intestinal enterocytes at chronic and single exposure to low power ionizing radiation

S. V. Кhуzhnyak¹, L. K. Bezdrobna², L. I. Stepanova³, V. S. Morozova¹, V. M. Voitsitskіy^1
1State Institution “National Research Center for Radiation Medicine of the National Academy of MedicalSciences of Ukraine”, Melnykov str., 53, Kyiv, 04050, Ukraine
²Institute for Nuclear Research of National Academy of Sciences of Ukraine, prospekt Nauky, 47, Kyiv,03680, Ukraine
³Taras Shevchenko National University of Kyiv, Volodymyrska st., 60, Kyiv, 01033, Ukraine

Objective – to investigate the intensity of oxidation and phosphorylation processes in the small intestine enterocytes mitochondria of the rats under chronic and single exposure to ionizing radiation of low power.
Materials and methods. The single irradiation of the rats with X-rays was performed using the RUM-17 equipment (at the dose of 0.055 Gy/min) for absorbed doses of 0.1; 0.5 and 1.0 Gy. The functional state of mitochondria was evaluated in 1 h and 24 h after irradiation. The chronic external γ-irradiation (at the dose rate of 0.72 cGy/min to achieve a total dose of 0.3; 0.6 and 1.0 Gy was performed using the “Etalon” equipment which contained 60Co. The intensity of the oxidation and phosphorylation activity of the small intestine enterocytes mitochondria was assessed by the polarographic method.
Results. The use of malate as exogenous substrate allowed to assess the functioning of all areas of the electron transport chain of mitochondria in experimental conditions. The increase in the intensity of mitochondrial respiration was found in all conditions and terms of research in response to irradiation. In chronic ionizing radiation appears partial separation of interface processes of oxidation and phosphorylation, as evidenced by the decrease in value of the index control and ADP / O and reducing efficiency phosphorylation (decrease of value Vf). For single exposure disconnection of coupling processes oxidation and phosphorylation were not accompanied by changes in the index of oxidative phosphorylation, however, was characterized by reduced ratio V4S/V4АТP.
Conclusions. Single and chronic exposure to low power of ionizing radiation leads to an increase in intensity of respiration and disruption of oxidative phosphorylation as a result of separation of interface processes of oxidation and phosphorylation. In chronic exposure received changes were accompanied by inhibition of ATP from ADP and FN because no change of ATP hydrolase activity of mitochondria was noticed. The identified functional disruption of enterocytes mitochondria by ionizing radiation may be associated with structural and functional changes of the respiratory chain, activity both enzymes of electron transport chain and H+-ATPase. Effects of ionizing radiation of low power can lead to disruption of mitochondrial bioenergetic function – one of the earliest manifestations of cellular dysfunction.
Key words: ionizing radiation, low power, single and chronic exposure, mitochondria, electron transport chain.
Problems of radiation medicine and radiobiology. 2014;19:482-489.