Kinetics of the reaction between nitric oxide and glutathione: implications for thiol depletion in cells.

Journal article

Nitric oxide in the absence of oxygen was suggested to react with 5-50 mM glutathione (GSH) over many minutes when [NO*] << [GSH] (N. Hogg et al., FEBS Lett. 382:223-228; 1996). However, Aravindakumar et al. (J. Chem. Soc. Perkin Trans. 2:663-669; 2002) provided data suggesting approximately 200-fold higher reactivity under conditions of [NO*] >> [GSH]. To help resolve these differences, the rate of loss of NO* ( approximately 9 microM) in aqueous solutions of GSH (2.5-20 mM) was measured by chemiluminescence. An apparent second-order rate constant of 0.080 +/- 0.008 M(-1) s(-1) at pH 7.4, 37 degrees C, was calculated based on the total [GSH] and "pseudo-first-order" kinetics; thiolate anion was much more reactive than undissociated thiol. These data imply a half-life of approximately 30 min for low concentrations of NO* with 5 mM GSH, 37 degrees C, pH 7.4, in the absence of oxygen. Possible kinetic schemes that can partially explain the divergent literature reports are discussed, notably an equilibrium in the reaction between NO* and GSH. Human breast carcinoma MCF-7 cells were exposed to NO* (initially approximately 18 microM) in alidded six well plate in an anaerobic chamber in vitro; intracellular GSH levels decreased by half in approximately 60 min. Aerobic exposure depletes GSH in cells in vitro much faster because of autoxidation of NO* to NO2*, >10(8) times more reactive toward GSH.

Authors: Folkes, L; Wardman, P

• Journal: Free radical biology and medicine
• Volume: 37
• Issue: 4
• Pages: 549-556
• Publication date: 2004-08-01
• DOI: 10.1016/j.freeradbiomed.2004.05.012
• EISSN: 1873-4596
• ISSN: 0891-5849
• Language: English
• Keywords: Animals; Hydrogen-Ion Concentration; Cell Line, Tumor; Time Factors; Models, Chemical; Rats; Nitrogen Dioxide; Oxygen; Sulfhydryl Compounds; Free Radicals; Humans; Glutathione; Temperature; Nitric Oxide; Dose-Response Relationship, Drug; Kinetics