The role of N-acetylcysteine in protecting synovial fluid biomolecules against radiolytically-mediated oxidative damage: A high field proton NMR study

High field proton (H-1) NMR spectroscopy has been employed to evaluate the abilities of the antioxidant thiol drug N-acetylcysteine and exogenous cyst eine to protect metabolites present in intact inflammatory synovial fluid s amples against oxidative damage arising from gamma-radiolysis (5.00 kGy) in the presence of atmospheric O-2 Although oxidation of urate to allantoin b y radiolytically-generated (OH)-O-. radical was readily circumventable by p re-treatment of synovial fluids with N-acetylcysteine (1.00 or 3.00 x 10(-3 ) mol.dm(-3)) or cysteine (1.00, 2.00 or 5.00 x 10(-3) mol.dm(-3)), both th iols offered only a limited protective capacity with respect to hyaluronate depolymerisation and the production of formate from carbohydrates in gener al. Radiolytic products generated from the added thiols (predominantly thei r corresponding disulphides) were simultaneously detectable in H-1 Hahn spi n-echo spectra of gamma-irradiated synovial fluids, permitting a quantitati ve evaluation of the radioprotective capacity of these agents. It is conclu ded that the multicomponent analytical ability of high field H-1 NMR spectr oscopy provides much useful molecular information regarding mechanisms asso ciated with the radioprotectant actions of thiols in intact biofluids.