Role of interaction of metabolism paths of formaldehyde and nitrogen oxide in the mechanism of their toxic effect. 2. Toxic effect of nitrogen oxide

Toxic properties of NO in organism are realized under its hyperproduction and inhibition of the system of anti-oxidant protection as a result of complex chemical transformations, the transient metals, oxygen, superoxide and other radicals being their main participant. Here direct paths (through formation of nitrosil complexes with the gem and nongem iron) of the toxic action of NO and the path mediated by active forms of nitrogen are found, which disturb various biomolecules and subcellular component through the reactions of S- and N-nitrozation, nitration, oxidation, desamination and other reaction, cause metabolic disbalance and death of cells by the type of apoptosis or necrosis. A possible mechanism of the death of cells caused by NO was considered on the example of thymocytes. According to this mechanism one of early stages of this death is a decrease of the cell fund of AP, intensification of catabolism of adenine nucleotides and transformation of xanthine oxidoreductase from D-form (xanthine dehydrogenase) of O-forms (xantine oxidase) which catalizes formation of cytotoxic molecules of superoxide and hydroperoxide. This cytotoxic mechanism which includes transformation of xanthine oxidase system, is probably, universal and does not depend essentially on the starting factor.