Accession Number : ADA346291


Title :   Chromium Toxicity: Reductive Enzymes in Humans.


Descriptive Note : Final rept. 1 Apr 95-31 Mar 98


Corporate Author : MEDICAL COLL OF WISCONSIN MILWAUKEE


Personal Author(s) : Myers, Charles R.


Full Text : http://www.dtic.mil/dtic/tr/fulltext/u2/a346291.pdf


Report Date : 28 MAY 1998


Pagination or Media Count : 38


Abstract : Several humans displayed marked similarity in the rates and properties of chromium reduction catalyzed by hepatic microsomal enzymes. Kinetic parameters demonstrated significant rates of chromium reduction using chromium(VI) concentrations anticipated for occupational exposure, and the reactive intermediate chromium(V) was formed. Room air inhibited only a minority of total chromium(VI) reduction. Iron, at concentrations well below that of chromium(VI), markedly stimulated the rates and V(max) of chromium(VI) reduction in both liver and lung, but did not significantly change other parameters. The iron effect was not altered by O2. Individuals who are simultaneously exposed to chromium and iron, or other compounds that mediate iron release from ferritin, are likely at greater risk for chromium toxicity. Cytochromes P450 and flavin-containing monooxygenase (FMO3) were not capable of mediating chromium(VI) or iron(III) reduction. P450 reductase was a poor mediator of reduction on its own, but played a significant participatory role in chromium(VI) reduction. Cytochrome b(5) significantly stimulated rates of chromium(VI) reduction, probably by acting in cooperation with P450 reductase and b(5) reductase. All findings showed significant differences from existing rodent models, emphasizing the need to utilize human studies to understand chromium toxicity in humans.


Descriptors :   *TOXICITY , *ENZYMES , *CHROMIUM , STIMULATION(GENERAL) , HUMANS , PARAMETERS , IRON , LUNG , KINETICS , EXPOSURE(PHYSIOLOGY) , SPACE(ROOM) , LIVER , RODENTS , MICROSOMES , FERRITIN.


Subject Categories : BIOCHEMISRTY
      TOXICOLOGY


Distribution Statement : APPROVED FOR PUBLIC RELEASE