Glutathione oxidation under the action of sodium nitrite on hemoglobin

The reaction of oxidation of oxyhemoglobin (oxyHb) to methemoglobin (metHb) by sodium nitrite in the presence of reduced glutathione is characterized by the changed ratios between the slow and rapid reaction phases. The duration of the lag phase increases as the glutathione concentration in the solution rises. The autocatalytic phase was inhibited and glutathione was oxidized to the disulfide form. The decreased rate of the reaction of oxyHb oxidation by sodium nitrite may be due to the effects of both the intermediate and the end products of oxidized glutathione. It is suggested that the thyil radical interacts to form the intermediate compound, anione glutathione disulfide (GSSG), which reduces metHb, thus increasing the lag phase duration. The autocatalytic phase inhibition can also be induced by electron transfer from the superoxide anion to the GSSG form. In addition to the GSSG, S-nitrosoglutathione was also formed during oxyHb oxidation by nitrite. In the absence of oxyHb in the neutral neutral medium, reduced glutathione (GSH) was not essentially oxidized by sodium nitrite. At pH lower than 6.0 S-nitrosoglutathione was observed to be formed due to the interaction of sodium nitrite with GSH. The addition of salts or increased pH of the solution induced hydrolysis of the product.