Production Of Bioactive NO From The Reaction Of Met-nitrite Hemoglobin With NO: Use Of Glassy Matices And Sol-gels

Abstract

There is growing evidence that nitrite-mediated reactions of Hb can generate bioactive forms of nitric oxide. The nitrite reductase reaction in which deoxy Hb reacts with nitrite has been studied from this perspective; however, this reaction generates NO under conditions where it can be easily scavenged. In contrast the proposed reaction of NO with nitrite bound to ferric heme derivatives to generate N2O3 is a much more promising mechanism. This follows because N2O3 can rapidly react with thiol containing peptides such as glutathione to produce S-NO derivatives. These species are likely to be the relatively long lived bioactive forms of NO that produce positive physiological effects in the vascular endothelium as occurs for blood substitutes derived from PEGylated Hb. We present results obtained using Hb samples encased in either glassy matrices or sol-gels that directly support this model. In particular there is spectroscopic evidence for the formation of a ferrous intermediate resulting from the direct reaction of NO with met-nitrite derivatives that precedes the formation of either ferrous NO or ferrous CO derivatives. This intermediate is attributable to a ferrous N2O3 complex.