Toxicological Sciences, Vol 52, 20-25, Copyright © 1999 by Society of Toxicology
FM Tatum and RD Hood
Biotransformation by methylation to monomethylarsonic acid (MMA) and
dimethylarsinic acid (DMA) influences inorganic arsenical toxicity, which
is often investigated in cultured cells. Arsenic (III) uptake and
methylation was assessed in rat hepatocytes in primary culture and in three
established rat cell lines (hepatoma-derived McA-RH 7777 cells and
H4-II-EC-3 cells, and kidney epithelium-derived NRK-52E cells) to compare
their use as model systems for arsenite metabolism. Incubation of all cell
types with 0.27, 0.67, 1.33, 2.67, or 6.67 microM As(III) concentrations
resulted in concentration-dependent arsenic uptake and biomethylation.
Arsenic uptake by the NRK-52E cells was initially slower than that of the
other cells, but by 8 h, total uptake was similar in all cell types. At the
lowest arsenite concentration, the percentages of total arsenic methylated
to MMA and DMA by the hepatocytes and the McA-RH 7777 cells were similar
(67 and 66%); methylation by the H4-II-EC-3 cells was somewhat lower (52%),
and methylation by the kidney-derived NRK-52E cells was much lower (15%).
Total arsenic methylation was inhibited in the cell lines, but not in the
hepatocytes, at the highest arsenite concentrations. In all cases, exposure
to increased arsenite concentrations inhibited conversion of MMA to DMA
much more than it affected the initial methylation step (inorganic arsenite
to MMA). These results indicate that rat hepatocytes in primary culture and
established rat hepatoma-derived cell lines are similar in their abilities
to accumulate and methylate arsenic to MMA and DMA at environmentally
relevant arsenic concentrations in the medium. They differed from the
kidney epithelium- derived cells, which exhibited substantially lower
biomethylation activity.
ARTICLES
Arsenite uptake and metabolism by rat hepatocyte primary cultures in comparison with kidney- and hepatocyte-derived rat cell lines
United States Department of Agriculture, National Animal Disease Center, Ames, Iowa 50010, USA.
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