Ultrasound-Induced Formation of S-Nitrosoglutathione and S-Nitrosocysteine in Aerobic Aqueous Solutions of Glutathione and Cysteine

I. I. Stepuro^1*, R. I. Adamchuk¹, T. P. Piletskaya¹, V. I. Stepuro², and S. A. Maskevich²

¹Institute of Biochemistry, National Academy of Sciences of Belarus, Bulvar Tarashkevicha 50, Grodno, 230017 Belarus; fax: (0152) 33-2141; E-mail: stepuro@grsu.grodno.by

²Kupala State University of Grodno, ul. Ozheshko 22, Grodno, 230023 Belarus

^* To whom correspondence should be addressed.

Received March 6, 2000; Revision received August 10, 2000

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S-Nitrosocompounds are formed when aqueous solutions of cysteine or glutathione are exposed to ultrasound (880 kHz) in air. The yield of the S-nitrosocompounds was as high as 10% for glutathione and 4% for cysteine of the initial thiol concentrations (from 0.1 to 10 mM) in the aqueous solutions. In addition to the formation of S-nitrosocompounds, thiol oxidation to disulfide forms was observed. After the oxidation of over 70% of the sulfhydryl groups, formation of peroxide compounds as well as cysteic acid derivatives was recorded. The formation of the peroxide compounds and peroxide radicals in the ultrasound field reduced the yield of S-nitrosocompounds. S-Nitrosocompounds were not formed when exposing low-molecular-weight thiols to ultrasound in atmospheres of N₂ or CO. In neutral solutions, ultrasound-exposed cysteine or glutathione released NO due to spontaneous degradation of the S-nitrosocompounds. N₂O₃, produced due to the spontaneous degradation of the S-nitrosocompounds in air, nitrosylated sulfhydryl groups of glutathione manifested in the appearance of new absorption bands at 330 and 540 nm. The nitrogen compounds formed in an ultrasound field modified the sulfhydryl groups of apohemoglobin and serum albumin. The main target for ultrasound-generated oxygen free radicals were cystine residues oxidized to cysteic acid residues.

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KEY WORDS: nitric oxide, nitrite, N₂O₃, S-nitrosocysteine, S-nitrosoglutathione, S-nitrosoalbumin, S-nitroso-apoHb, cysteic acid, ultrasound, pyrene fluorescence, cystine oxidation, fluorescence quenching

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