Abstract: | The biological fate of a chelated vanadium source is investigated by/n vivo spectroscopic methods to
elucidate the chemical form in which the metal ion is accumulated. A pulsed electron paramagnetic
resonance study of vanadyl ions in kidney tissue, taken from rats previously treated with
bis(ethylmaltolato)oxovanadium(IV) (BEOV) in drinking water, is presented. A combined approach using
stimulated echo (3-pulse) electron spin echo envelope modulation (ESEEM) and the two dimensional 4-pulse
hyperfine sublevel correlation (HYSCORE) spectroscopies has shown that at least some of the VO2+ ions are
involved in the coordination with nitrogen-containing ligands. From the experimental spectra, a 4N hyperfine
coupling constant of 4.9 MHz and a quadrupole coupling constant of 0.6 + 0.04 MHz were determined,
consistent with amine coordination of the vanadyl ions. Study of VO-histidine model complexes allowed for
a determination of the percentage of nitrogen-coordinated VO2+ ions in the tissue sample that is found
nitrogen-coordinated. By taking into account the bidentate nature of histidine coordination to VO2+ ions, a
more accurate determination of this value is reported. The biological fate of chelated versus free (i.e. salts) vanadyl ion sources has been deduced by comparison to earlier reports. In contrast to its superior pharmacological efficacy over VOSO4, BEOV shares a remarkably similar biological fate after uptake into kidney tissue. |