FORMATION OF S-NITROSO COMPOUNDS FROM SODIUM-NITROPRUSSIDE, NITRIC-OXIDE OR NITRITE AND REDUCED THIOLS - ANALYSIS BY CAPILLARY ISOTACHOPHORESIS

Sodium nitroprusside (SNP) is a potent, rapidly acting intravenous hypotensive agent. The direct action on blood vessels is thought to be due to its nitroso (NO) group. This suggestion is supported by the discovery of an endothelial relaxing factor, most probably being the radical nitric oxide (NO.) or a S-nitroso compound. In this paper we describe for the first time an analytical capillary isotachophoretic (ITP) method for the determination of SNP, of some potent vasodilating and platelet anti-aggregatory S-nitroso compounds from biological and pharmacological precursors, and of their final metabolites nitrite and nitrate. ITP was applied to study SNP stability in aqueous solutions and chemical formation of S-nitroso compounds by the reaction of reduced thiols such as N-acetyl-L-cysteine, glutathione and N-acetyl-D,L-penicillamine with SNP at pH 7.4. We found that these thiols react spontaneously with SNP to give the corresponding S-nitroso compounds. This result suggests that the vasodilating and anti-aggregatory properties of SNP may be in part due to the formation of S-nitroso compounds from SNP.