Detection of short-lived free radicals by low-frequency electron paramagnetic resonance spin trapping in whole living animals.
We report the direct observation of sulfur trioxide anion free radical (SO3.-) from the body of live mice by using a low-frequency (1.2 GHz, L-band) EPR spin trapping method. Intraperitoneal injection of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) (15 mmol/kg) used as trapping agent was followed by sequential iv injections of sodium sulfate (2-5 mmol/kg) and sodium dichromate (0.3 mmol/kg). The mouse was placed in an L-band loop gap resonator. The observed spectra consisted of two superposed components: DMPO/SO3.- (alpha N = 14.0, alpha H = 16.0) and Cr(V) (g = 1.9798). The time course for the generation and reduction of DMPO/SO3.- was followed. The signal intensity reached a maximum at about 7 min. In vitro experiments carried out at 9.15 GHz confirmed the production of SO3.- under the conditions used for in vivo studies; the hyperfine splittings of DMPO/SO3.- produced in the in vitro experiments were the same as those produced in the in vivo studies. The production of SO.-3 is supported by oxygen uptake studies, which show that the prior addition of 300 mM DMPO inhibits oxygen consumption by SO3.-.
Jiang
J
J
Department of Radiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Liu
K J
KJ
Shi
X
X
Swartz
H M
HM
D000818:Animals; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals / Q000032:analysis*; D051379:Mice; D013461:Sulfur Oxides / Q000378:metabolism*
D005609:Free Radicals; D013461:Sulfur Oxides; C011118:sulfur trioxide