Effect of heparin on viologen-stimulated enzymatic NADH depletion

Paraquat and diquat undergo redox cycling mediated by xanthine oxidase in the NADH-dependent manner. In these processes, the rates of NADH oxidation and superoxide formation are increased almost 10-fold. The addition of heparin can substantially inhibit these processes. A protective role of heparin against oxygen radicals formation can be rationalized in terms of its ability to bind paraquat or diquat. The binding process has been investigated by means of the pulse radiolysis technique. Biological consequences of the binding processes are discussed.