[Vascular reactivity and metabolism of the reactive oxygen species and nitrogen in effects of low doses of radiation].

The disturbance of endothelium-dependent and endothelium-independent vascular reactions of relaxation was registered in the preparations of aorta of radiosensitive BALB/c mice, exposed to chronic external gamma-irradiation (cumulative dose of 0.43 Sv). Low doses of radiation induced an intensive hydrolysis of membrane phospholipids by phospholipase A2, displayed by an increase in the level of eukosanoisds--LTC4 and TxB2, formed under effects of lipid oxidases (lipoxygenase and cyclooxygenase) at the same time with O2 generation. High doses of O2- can also be formed under the effect of low doses of radiation along xanthine oxidase pathway simultaneously with uric acid. In these conditions *OH-radical is formed not only at the expense of water radiolysis, which is observed under the effect of high doses, as well as along the two--NO-dependent and NO-independent--pathways. Significant increase in the content of lipid peroxidation products--dienic conjugates and valonic dialdehyde--in the organs of cardiovascular system is a confirmation of active generation of *OH and *NO2 under the effect of low doses of radiation. The latter induce significant changes in the pools of NO stable metabolites, which can cause disturbance of NO-dependent physiological functions of both heart and aorta. Significant decrease in the levels of nitrite and nitrozothiols in these conditions may result in an oxidative stress. In increased simultaneous generation of *O2- and NO they may bind and thus form a toxic substance peroxynitrite. This notion can be confirmed by the low doses of nitrite, which are formed spontaneously in the presence of molecular oxygen against the background of increased or control levels of nitrate, which is formed mainly at the degradation of peroxynitrite, i.e. at high levels of superoxide anion.