Nitrite May Be an Important EDRF Modulator.

Recently many studies suggested that S-nitrosothiols instead of active nitric oxide are EDRF. The studies showed that reduced thiols could not react directly with.NO at physiological pH (7.4) to form S-nitrosothiols but oxidized to nitrite which is very stable at pH 7.4. In contrast at low pH nitrite reacted rapidly with reduced thiols to form S-nitrosothiols. Similarly both nitrite and.NO gas reacted with deoxyHb and oxyHb at low pH but not at pH 7.4 to form HbFeII-NO complex or metHb and nitrate. The pH is a key factor to control this nitrosation process which is determined in vivo by oxygen tension and redox status. From these results a hypothesis is proposed that nitrite may be an EDRF modulator which controls the nitrosation level of reduced thiols in biological system.