ABSTRACT

Life began in the absence of oxygen. However due to photosynthetic activity (by splitting of water) oxygen became present in the atmosphere. Due to the increasing efficiency of energy storage by ATP, most organisms developed and depended on oxygen as the final electron acceptor. Unfortunately oxygen is also responsible for the metabolic formation of some highly toxic and reactive by-products, namely the formation of O2

tage gained has to be paid for by some disadvantage, in other words Athere is no such thing as a free lunch@. As suggested by Sies [393], biological systems are in a state of approximate equilibrium between prooxidant forces and the antioxidant capacity of most biological systems. Our cells, tissues and orgens function within very narrow limits of oxygen tension, pH, Fe (III), Cu(II), Ca(II), thiols, and enzymes, such as SOD and external antioxidants (ascorbic acid, tocopherols, and selenium). Among the radicals O2@

! and @NO we encounter the same situation: too little or too much may have deleterious consequences. Biological oxygen metabolizing systems are maintaining a precarious balance between life and death. The prooxidant forces are likely to be predominant, otherwise we may not age nor die. A well-known measure for oxidative damage is the accumulation of lipofucsin during the lifespan of an organism. Lipofucsin is a PUFA derived colored oxidation product. Oxidative stress causes extensive damage, including lipid peroxidation of membranes, oxidation of proteins, and damage to DNA and RNA. I have discussed the basic chemistry of ROMs in previous chapters. All we have to do now is apply this knowledge to the interpretation of some pathological processes.