Analysis of nanomolar S-nitrosothiol concentrations in physiological media.

S-Nitrosothiols occur endogenously and are thought to function as storage forms and/or stable carriers of nitric oxide. Moreover, the S-nitrosothiols have been postulated to function as neurotransmitters and mediate the vasodilator action of glyceryl trinitrate. Because of the increasing pharmacological and physiological interest in S-nitrosothiols, a sensitive method for analysis of these substances is required. We describe a sensitive method based on adsorptive stripping voltammetry for measurement of two S-nitrosothiols, namely, S-nitroso-N-acetyl-D-penicillamine (SNAP) and S-nitrosoglutathione (SNOG), in Krebs' solution. The method is based on the irreversible electrochemical reduction of SNAP and SNOG at the hanging mercury drop electrode (HMDE). The analytes were adsorbed at the HMDE for 60 s at -0.100 V, then exposed to a cathodic linear potential scan of 100 mV s(-10) which resulted in the reduction of SNAP at -0.470 V and SNOG at -0.530 V. Under these conditions, 4 nM SNAP and 11 nM SNOG were readily quantified. Using the above method, we were able to confirm the rapid degradation of SNAP under UV irradiation. Reproducibility of the method as applied to the analysis of these S-nitrosothiols in Krebs' solution was demonstrated by the within-day and day-to-day coefficients of variation of 1.5% and 2.0%, respectively.