C L Chen

Oregon State University, Corvallis, Oregon, United States

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Publications (3)11.72 Total impact

  • C L Chen · P D Whanger
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    ABSTRACT: The effects of selenium and arsenic on metallothionein (MT) levels were determined in vitamin B12-supplemented and depleted rats. The binding of selenium and arsenic to MT in vitro and in vivo was also investigated. Rats fed a vitamin B12-deficient diet had significant (p < 0.05), higher levels of liver MT as compared to vitamin B12-supplemented rats. Rats fed 5-9 micrograms/g selenium as selenite or 50-150 micrograms/g arsenic as arsenite showed no significant increase of MT content in the liver. However, significant increases in MT levels in liver (p < 0.01) and kidney (p < 0.05) were seen when rats were injected with 1.5 mg selenium as selenite, and increase of liver MT levels (p < 0.05) was shown when injected with 5 mg arsenic as arsenite/kg body weight. In comparison to zinc, injection of selenium or arsenic caused only a slight elevation of liver MT levels. Liver cytosolic Sephadex G-75 patterns of rats injected with both zinc and arsenic gave separate peaks for arsenic and zinc which suggest that in vivo arsenic binding to MT may be insignificant. Spectrophotometric absorption changes at 255 nm with various levels of selenium or arsenic additions to an MT solution were used to show that selenite gave a maximum absorption increase at a 1:1 molar ratio, but maximum absorption change occurred with arsenite at a molar ratio of 7:1.
    No preview · Article · Jun 1994 · Journal of Inorganic Biochemistry
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    ABSTRACT: Following injection with [75Se]selenite, a low molecular weight 75Se-selenocysteine containing protein was purified from rat muscle. The purification procedure involved ammonium sulfate fractionation, Sephadex G-50 gel filtration, cation exchange chromatography on CM-Sephadex, and reverse phase high pressure liquid chromatography using a C-18 Vydac column. Four forms of the protein were separated by the cation exchange and reverse phase chromatography steps. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry of the four proteins revealed masses of 9550 +/- 1, 9596 +/- 1.2, 9858 +/- 1.3, and 9898 +/- 1.1 daltons. Glutamate, glycine, lysine, leucine, and valine are the major amino acids in this protein. About 0.92 g atoms of selenium was found per g mol of protein, and this selenium was present as selenocysteine. Thus, this appears to be a new selenoprotein, and we have named it selenoprotein W.
    Full-text · Article · Sep 1993 · Journal of Biological Chemistry
  • C.L. Chen · P.D. Whanger
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    ABSTRACT: Animals are known to convert inorganic selenium to less toxic methylated compounds such as dimethylselenide (DMSe) and trimethylselenonium (TMSe). This study investigated the role of vitamin B12, a cofactor of methionine synthetase, in selenium methylation in the rat. Vitamin B12-depleted rats expired 16% of dosed 75Se-selenite as DMSe compared to 45% for control rats and excreted less TMSe in the urine (6.1% of dose) than control (9% of dose) rats. At the same time, higher (p < 0.05) tissue (liver, kidney, muscle) selenium levels and lower (p < 0.05) blood selenium levels were found in vitamin B12-deficient rats. Primary hepatocytes from vitamin B12-deficient rats volatilized 15% of selenite in incubation medium in 5 hr as compared to 49% in hepatocytes from control rats. Hepatocytes from vitamin B12-deficient rats were less resistant to selenite toxicity. In vitro methylation of selenium with liver extract from vitamin B12-deficient rats showed one-third to one-half the rate of volatilization of selenium as compared to control rats. S-adenosylmethionine was required for this reaction. These results show that vitamin B12 deficiency significantly decreases the ability of rats to methylate selenium.
    No preview · Article · Jan 1993 · Toxicology and Applied Pharmacology