IN-VITRO REDUCTION KINETICS OF HEXAVALENT CHROMIUM IN HUMAN BLOOD

This study examines time- and concentration-dependent changes in distr ibution of hexavalent chromium [Cr(VI)] and total chromium [Cr-(TOT)] in reconstituted human blood following addition of potassium dichromat e. Fresh human blood stabilized with EDTA was obtained from human volu nteers soon after meal ingestion and at 2.5 h after a light meal (here in defined as ''2.5-h fasted'' conditions). Cr(VI) spiked into plasma under 2.5-h fasting conditions at 3.0-12.5 mu g/L was stable for sever al hours, indicating a lack of appreciable reductive capacity in isola ted plasma. Spiked plasma following a recent meal exhibited immediate but variable reduction of Cr(VI) up to 300 mu g/L. When the spiked pla sma was recombined with the red blood cell (RBC) fraction, rapid reduc tion occurred in both the plasma and the RBC fractions based on measur ement of Cr(VI) and Cr(TOT). The data indicate that plasma reduction c apacity is enhanced by a recent meal, but may be overwhelmed at Cr(VI) concentrations between 2000 and 10,000 mu g/L. These data also sugges t that the RBC fraction apparently has the capacity to reduce Cr(VI) a t concentrations in blood up to 15,000 mu g/L, and that the rate of Cr (VI) uptake into RBCs may not exceed the rate of intracellular reducti on at these concentrations. (C) 1998 Academic Press.