Reaction of nitric oxide with hydrogen peroxide to produce potentially cytotoxic singlet oxygen as a model for nitric oxide-mediated killing.

Nitric oxide, as well as being a major regulator of vascular reactivity, has been shown to be one of the mediators of cytotoxicity in macrophages. This cytotoxic effect seems to be due to the interaction between nitric oxide and oxygen-related free radicals. This study shows that, in vitro, nitric oxide reacts with hydrogen peroxide to release large amounts of chemiluminescence with the characteristics of the highly cytotoxic species, singlet oxygen. This is supported by the observation that when nitric oxide was added to a superoxide generating system, catalase inhibited the production of singlet oxygen while superoxide dismutase enhanced it.