EPR evidence for nitric oxide production from guanidino nitrogens of l-arginine in animal tissues in vivo

l‐Arginine depletion by arginase reduces nitric oxide production in endotoxic shock: an electron paramagnetic resonance study

“…2b--d). The EPR spectrum now displayed the characteristic three-line s~-ctrum of NO-FeDETC2 similar to that demonstrated previ-¢,usly by other workers [18,22], at gz = 2.02, gyx = 2.035, with 't triplet hyperfine structure (a = 1.3 mT) at gyx, due to the interaction of the unpaired electron on the ~4N nucleus of NO complexing with free FeDETC2 (see Fig. 2).…”

“…2a shows the g = 2 region of the EPR spectrum of spleen removed from a rat treated with FeDETC2 only. At 15 K, the tissue exhibited an intense quartet signal at -321.6, 326.0, 331.0, 336.1 mT (a~-4.9 mT), characteristic of DETC complexed with endogenous copper [18]; this signal was detected at temperatures up to 100 K. A weaker signal to higher field at g-~ 1.94 was also present in the spectrum and assigned to reduced iron-sulphur proteins. Endotoxin administration to the rat resulted in the detection of a prominent new signal in the g = 2 region, from spleen, liver, kidney and lung (Fig.…”

“…First, to obtain an indirect measure of whole body NO synthesis, we measured the accumulation of nitrite and nitrate, the stable end-products of NO, in the plasma. Secondly, in order to detc:~nine the extent of NO synthesis in individual organs we used EPR spectroscopy to measure the NO adduct formed with the spin trap FeDETC2, a method which has previously been employed to measure organspecific NO synthesis in mice [18] and rats [22,24]. The insoluble complex remains in the tissues, and the size of the EPR signal obtained in the presence of FeDETC2 is related to the amount of nitric oxide synthesized during the 30-min period before the animals were killed.…”

“…Griffith et al [17] have provided evidence that it is possible to decrease NO synthesis in the guinea pig by using arginase to deplete plasma arginine. In the present study, we have investigated the effect of arginase on induced NO production by electron paramagnetic resonance (EPR) spectroscopy and the spin-trap iron(II) diethyldithiocarbamate (FeDETC2), recently developed by Vanin et al, and shown to specifically trap NO formed in animal tissues in rive [18]. NO generated in rats given LPS alone, LPS/L-NMMA or LPS/arginase was directly measured from the NO-FeDETC2 EPR signal observed from tissue homogenates.…”

The evolution of biomedical EPR (ESR)

“…In addition the paramagnetic gas NO is effectively EPR silent. However, it was shown by Vanin's group [62] and Lai and Komarov [63] that one can 'trap' NO as the ferrous iron complex in a coordination complex involving dithiocarbamates. The two most useful compounds are the water soluble, and the lipid soluble (blood brain barrier permeable).…”