How can we explain the significant decrease in GST activity, while there is no oxidative stress (significant decrease in MDA levels) and the GSH levels are normal? Also, SOD levels showed significant increases, while catalase activity showed significant decrease.
you cannot rule out oxidative stress due to significant low level of MDA. it could be the onset of oxidative effect hence GST serve as the first line of defense against the oxidative stress. Another explanation is that decrease in SOD could be as a result of saturation due to overwhelming peroxidation hence GST come into play. Where did you carried out the test, tissue or serum? Try to think in this line you may get the answer.
Dear Heba.
I dont understand the question. GSTs are responsible for detoxifying components after e.g. oxidative damages. So when you have no signs of oxidative stress (decrease in lipidperoxidation, why should the GST activity be increase?
By the way. It is not sufficient to just meseasure GSH levels, but the ratio between reduced and oxidized form (GSSG), and enzyme activities of the antioxidant capacities is also less expressive. I would interprete, that an increase of SOD activity would be a sign that more free radicels in form of superoxide anions are beeing generated, and that this may lead to an increase of hydrogen peroxide. This is also a reactive oxygen species that need to be detoxified either by catalase or gluthathion peroxidase. So when you demonstrate a significant decrease of CAT activity (and a normal and not a reduced level of GSH, no increase GPx activity) this would pointing towards an decreased detoxification of hydrogen peroxide. Would this not suggest an increased oxidative stress?
I think Charles is right by asking you what you are actually looking at (cells, tissues, plasma?). I have to admid that I am a fan of using H2-DCFH-DA for real ROS detection in living cells to estimate oxidative stress and antioxidant capacities. If possible, you should apply this substance in your experiments, it quite cheap and usefull.
Hope that this still may help you.
I agree with Nwonuma Charles & Julian Kamhieh-Milz. If there is no signs of oxidative stress , the GST activity would not be be increase or decrease.
GST as an enzyme has many detoxifying functions not related to oxidative stress, so it can change completely independently.
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