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Nitric oxide (NO) is one of the universal regulators of cell and tissue metabolism. Besides, it plays the role of one of the main cytotoxic effectors in cell immunity system. High reactivity of NO determines its short lifetime (several seconds) in organism. Low-molecular-weight S-nitrosothiols, S-nitrosocompounds of proteins, dinitrosyl compounds, along with nitrosohemoglobin, nitrosomyoglobin are more stable compounds than NO and probably create physiological depot of NO in organism. In this work it is shown that semiquinone and leuko forms of riboflavin (RF) interacted with S-nitrosoglutathione and buthylnitrite to release NO. Leuko form of RF was obtained under action of laser irradiation (λ = 337 nm, nitrogen laser) in the presence of electron donors (NADH, pyruvate). After mixing of reduced, uncolored leuko form of RF with nitrosoglutathione or buthylnitrite absorption spectrum underwent transformation which testified about RF oxidized form production. Simultaneously with RF oxidized form production growth of fluorescence with maximum at 533 nm occurred. Production of RF oxidized form due to interaction of S-nitrosoglutathione with leuko or semiqiuinone forms of RF was accompanied by formation of glutathione and release of NO. In the case of buthylnitrite butanol and NO were formed. Semiquinone form of RF was obtained under action of laser irradiation in anaerobic conditions on oxidized RF in the presence of bivalent metal ions [Zn (II), Mg (II)]. Semiquinone form of RF as well as leuko form transfer electrons to nitrosoglutathione molecules. This process is also accompanied by formation of glutathione, NO, oxidized RF. Obtained results testify that RF plays important role in NO metabolism due to interactions of its redox forms with S-nitrosocompounds and alkylnitrites which possibly can serve as components of NO physiological depot in organism.
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