Access Type

Open Access Thesis

Date of Award

January 2013

Degree Type


Degree Name



Nutrition and Food Science

First Advisor

Diane Cabelof


Reactive oxygen species and free radicals are associated with the negative effects of aging. Enzymatic and non-enzymatic mechanisms can defend cell structures from free radical damage. Selenium is an essential trace element necessary for cellular functions in the human body. A positive correlation between low serum selenium levels with the morbidity and mortality of a range of cancers has been illustrated in numerous studies. Glutathione Peroxidase catalyzes a reaction in which H2O2 oxidizes the reduced form of GSH and forms H2O. NADPH further reduces GSSG, the oxidized structure of glutathione, in a reaction catalyzed by glutathione reductase. Tissue culture was grown using mice fibroblasts in 3% oxygen and was supplemented with 30nM of sodium selenite. The activity of the glutathione peroxidase enzyme was indirectly measured by the rate of transformation of NADPH into NADP+ using a Glutathione Peroxidase Assay Kit. Results showed that GPx-1 activity was significantly increased (p<0.05) in selenium-supplemented culture media. By also comparing Tag92 and BNL-C2 cells, we can determine that amplified GPx-1 activity is not cell line specific. TAG92 cells had approximately a 5-fold significant increase (p<0.05) to GPx-1 activity. Finally, all cells were grown in 3% oxygen, which closely resembles the 2-5% oxygen concentration in tissue. TAG92 cells were grown in 20% oxygen for several weeks, treated with 250 fÝm of H202, and compared to cells grown in 3% oxygen. Cells grown in 20% O2 had a 3-fold significant increase (p<0.05) of glutathione peroxidase activity compared to cells grown in 3% O2. In conclusion, reactive oxygen species, A.K.A. oxidative stress, represent a possible toxic environment for human bodies. Glutathione peroxidase enzyme, found at the core of the selenium element, contributes in detoxification by reducing peroxides, scavenging free radicals, or by conjugating with electrophilic compounds.