Nitric oxide: prospects and perspectives of in vivo detection by L-band EPR spectroscopy

Abstract

This paper discusses, compares and evaluates various in vivo EPR methods of detection of nitric oxide (NO). In particular the various classes of agents are: Fe(II)-dithiocarbamate derivative complexes of MGD ( N-methyl-D-glucamine dithiocarbamate) and DTCS [ N-(dithiocarboxy)sarcosine], stable imidazolineoxy N-oxides and nitronyl N-oxides, and NO-sensitive chars. As a specific example direct, real-time, in vivo measurements of nitric oxide (NO) in mice are described with the water soluble metal chelator complex -, as monitored at L-band EPR. The three-line EPR spectrum of [--NO] was observed non-invasively in both control animals injected with the preformed product [--NO] and from lipopolysaccharide (LPS) treated mice subsequently injected with - complex. The [--NO] spectrum was markedly suppressed after administration of phenyl N-tert-butyl nitrone (PBN) prior to LPS injection as PBN inhibits the expression of inducible nitric oxide synthase (iNOS). When -arginine was administered to LPS-treated mice, an EPR spectrum consisting of both three- and two-line EPR signals (due to -- and -- respectively) was observed, confirming that the trapped NO was generated through the NOS enzyme and not other chemical routes.