LOW-FREQUENCY ELECTRON-PARAMAGNETIC-RESONANCE INVESTIGATION ON METABOLISM OF CHROMIUM(VI) BY WHOLE LIVE MICE

Detection of Cr(V) in the reduction of Cr(VI) by whole live mice and i ts characterization were carried out by low frequency electron paramag netic resonance (EPR). Intravenous injection of Cr(VI) to mice generat ed Cr(V). The Cr(V) was found predominantly in the liver with a small amount in the blood. Liver homogenates from Cr(VI) heated mice generat ed essentially the same Cr(V) spectrum as that obtained from the whole live mice. This Cr(V) species was identified to be a Cr(V)-nicotinami de adenine dinucleotide (NAD) (P)H complex with an oxygen bond to Cr(V ). Pretreatment of the mice with ascorbic acid and glutathione reduced the Cr(V) formation, while pretreatment with reduced nicotinamide ade nine dinucleotide (NADH) enhanced it. Metal chelators, ethylenediamine tetraacetic acid (EDTA), 1,10-phenanthroline, and diethylenetriaminepe ntaacetic acid (DTPA) inhibited the intensity of the Cr(V) signal. The results suggest that Cr(V) generated in the whole body of a live anim al is a Cr(V)-NAD(P)H complex and NAD(P)H/flavoenzymes and not glutath ione or ascorbate as the major one-electron Cr(VI) reductant responsib le for observed formation of Cr(V)-NAD(P)H complex in vivo.