X-band and S-band EPR detection of nitric oxide in murine endotoxaemia using spin trapping by ferro-di[N-[dithiocarboxy]sarcosine]

Ammonium salt of N-(dithiocarboxy)sarcosine (DTCS) chelated to ferrous salt was tested as an NO-metric spin trap at room temperature for ex vivo measurement of NO production in murine endotoxaemia. In a chemically defined in vitro model system EPR triplet signals of NO-Fe(DTCS)2 were observed for as long as 3 hours, only if samples were reduced with sodium dithionite. This procedure was not necessary for the ex vivo detection of NO in endotoxaemic liver homogenates at X-band or in the whole intact organs at S-band, whereas only a weak signal was observed in endotoxaemic lung. These results suggest that in endotoxaemia not only high level of NO, but also the redox properties of liver and lung might determine the formation of complexes of NO with a spin trap. Nevertheless, both S- and X-band EPR spectroscopy is suitable for NO-metry at room temperature using Fe(DTCS)2 as the spin trapping agent. In particular, S-band EPR spectroscopy enables the detection of NO production in a whole organ, such as murine liver.