ABSTRACT
The formulation of an integrated view on the role of key defense systems in determining target organ toxicity must deal with some crucial problems. Cytochrome P-450, the well-characterized terminal oxidase of the microsomal electron transport system, metabolizes not only endogenous substrates but also various exogenous organic compounds. Compounds which contain one or more hydroxyl groups are particularly good substrates for sulfate conjugation. The superoxide anion radical is generated in the living cell in enzymatic and nonenzymatic modes under physiological conditions. Catalase and glutathione (GSH) peroxidase are the major enzymes involved in the reduction of hydrogen peroxide. GSH-dependent protection against lipid peroxidation is exerted by factors present in the cytosol. Superoxide Dismutases, catalase, and GSH peroxidase are located in the hydrophilic milieu in the cell, to serve as the first defense prior to production of more reactive oxygen species such as the hydroxyl radical.
