QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ganther, H. E. Articles by Ip, C. Search for Related Content PubMed PubMed Citation Articles by Ganther, H. E. Articles by Ip, C.

---

Articles

Thioredoxin Reductase Activity in Rat Liver Is Not Affected by Supranutritional Levels of Monomethylated Selenium In Vivo and Is Inhibited Only by High Levels of Selenium In Vitro¹

Howard E. Ganther^* and Clement Ip²

^* Department of Nutritional Sciences, University of Wisconsin, Madison, Madison, Wisconsin 53706 and Department of Experimental Pathology, Roswell Park Cancer Institute, Buffalo, New York 14263

²To whom correspondence should be addressed at the Department of Experimental Pathology, Roswell Park Cancer Institute, Elm & Carlton Streets, Buffalo, NY 14263. E-mail: Clement.Ip{at}roswellpark.org

Thioredoxin reductase is a selenoenzyme responsible for maintaining thioredoxin in the reduced form. Because thioredoxin is involved in many cellular processes, thioredoxin reductase is likely to be an important regulatory protein for both normal and transformed cells. Monomethylated selenium compounds inhibit carcinogenesis. In the present study, we investigated whether methylated forms of selenium would alter thioredoxin reductase activity in rats. The liver enzyme was used as a model system. Se-methylselenocysteine and methylseleninic acid consumed by rats at 2 µg Se/g diet for 3, 6, 10 or 22 wk did not affect activity compared with a basal diet containing 0.1 µg Se/g. The direct addition of 50 µmol dimethyl diselenide or dimethyl selenenylsulfide per L to liver extracts significantly inhibited thioredoxin reductase activity by 60%. The magnitude of inhibition was dependent on the amount of thioredoxin in the assay and was reversible by dialysis, suggesting that a competitive type of inhibition occurs in vitro. Although thioredoxin reductase can be inhibited by high levels of selenium in a cell-free system, it should be noted that such a condition is unlikely to be attainable in vivo. Caution needs to be exercised in interpreting the in vitro results.

KEY WORDS: • thioredoxin reductase • methylated selenium compounds • in vivo study • in vitro study • rats.

This article has been cited by other articles:

				X. Wang, J. Zhang, and T. Xu Cyclophosphamide-evoked heart failure involves pronounced co-suppression of cytoplasmic thioredoxin reductase activity and non-protein free thiol level Eur J Heart Fail, February 1, 2009; 11(2): 154 - 162. [Abstract] [Full Text] [PDF]

				D. N. Stemm, J. C. Tharappel, H.-J. Lehmler, C. Srinivasan, J. S. Morris, V. L. Spate, L. W. Robertson, B. T. Spear, and H. P. Glauert Effect of Dietary Selenium on the Promotion of Hepatocarcinogenesis by 3,3', 4,4'-Tetrachlorobiphenyl and 2,2', 4,4', 5,5'-Hexachlorobiphenyl Experimental Biology and Medicine, March 1, 2008; 233(3): 366 - 376. [Abstract] [Full Text] [PDF]

				J. Zhang, V. Svehlikova, Y. Bao, A.F. Howie, G. J. Beckett, and G. Williamson Synergy between sulforaphane and selenium in the induction of thioredoxin reductase 1 requires both transcriptional and translational modulation Carcinogenesis, March 1, 2003; 24(3): 497 - 503. [Abstract] [Full Text] [PDF]

				S. Gromer and J. H. Gross Methylseleninate Is a Substrate Rather Than an Inhibitor of Mammalian Thioredoxin Reductase. IMPLICATIONS FOR THE ANTITUMOR EFFECTS OF SELENIUM J. Biol. Chem., March 15, 2002; 277(12): 9701 - 9706. [Abstract] [Full Text] [PDF]