Free radicals defences against

Evidence for the Existence of Free 3. Defences against Free-radical Attack 77... 

Ascorbate has multiple antioxidant capacities and may be the most important water-soluble defence against free-radical damage in human plasma. At millimolar concentrations, ascorbate scavenges O2, OH and HOCl (Blake et al., 1983). The latter reaction protects plasma lipids against degradation by activated PMNs. 

Diplock, A.T., Defence against reactive oxygen species. Free Radical Res., 29, 463, 1999. 

De Vos et al. (1989) suggest that the copper-induced damage to the permeability barrier in roots of Silene cucubalus is caused by a direct metal action on both membrane lipids and thiols. They propose that the first damaging effects of copper ions is the oxidation and cross-linking of membrane protein sulphydryls. However, they also adjudge an important role to the copper induced membrane lipid peroxidation, possibly due to direct free radical formation in the membrane this effect could be enhanced by a depletion of thiols such as glutathione which results in a concomitant decrease of the cellular defence system against free radicals. 

As an indirect effect of increased metal uptake, the physiological state of the cell can alter and defence mechanisms can be induced. Phytochelatin (metal binding proteins) synthesis and induction of free radical quenching enzymes and metabolites were frequently observed. Especially the latter can protect membranes against oxidative breakdown. 

An elaborate cellular defence system against oxygen-free radical toxicity exists, which includes, in a first line, factors that prohibit the formation of, or scavenge primary initiators of the lipid peroxidation process, such as metal-ion-binding proteins or the enzymes superoxide dismutase (SOD),... 

Hayes JD, McLeUan LI. Glutathione and glutathione-dependent enzymes represent a coordinately regulated defence against oxidative stress. Free Radic Res 1999 31 273-300. 

Fridovich, I. (1979). Superoxide dismutases defence against endogenous superoxide radical. In Oxygen Free Radicals and Tissue Damage. Excerpta Medica, New York, pp. 77-94. 

Defence mechanisms against free radicals and reactive oxygen species... 

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