I want to measure the activities of catalase, superoxide dismutase, MDA, glutathione peroxidase. Which sample is best for this? Serum or tissue homogenates?
it depends what are you interested in: plasma levels indicate systemic status, levels in tissue homogenates give information on local status in organs,
katka
It may depend on the animal model and whether you have used any drug/ formulation to treat the model. In case of subcutaneous/ injected/ oral administration of drug it would be better to use tissue rather using serum. But for preliminary study you may use serum.
It depends on the objective of your study. But in my opinion I think that it’s much better to measure the enzymatic and non-enzymatic antioxidant activities in serum as preliminary study and in tissue homogenates as a detailed study to know the mechanisms involved in it.
If you want to know the general antioxidant status, you could determine the antioxidant activity in serum (ORAC, ABTS). However, if you would like to be more specific, you could measure the activity of the antioxidant enzymes in the homogenates of a specific tissue.
If you are conducting a fundamental research then you need to determine the state of antioxidant / prooxidant systems in the blood and in the organs (most often in the liver, kidneys, brain, heart). But, if you want to determine the general state of the body, it is enough to determine in the blood. Note that the activity of catalase in blood determination is carried out in whole blood, and not its plasma. All other indicators are determined in blood plasma.
In my opinion, it´s depends on the objective are you looking for your study. I think it’s better to measure the enzymatic and non-enzymatic antioxidant activities in serum at first as preliminary study and then in tissue homogenates to know the mechanisms involved.
I will go for blood to get a whole picture for enzymatic and non-enzymatic antioxidant status then you can perform them in some selective tissue homogenates specially liver
Tissues give better results for local stress. Liver homogenate for diabetes and kidney homogenates for kidney pathologies, brain homogenates for the stress in the brain. But if you re dealing with systemic diseases, blood may give a broader picture of the whole body oxidative stress levels.
Moreover, the membrane extractions give far more precise results compared to the tissue crude homogenates which is the scramble of whole tissue including lytic enzymes harming the tissue more than oxidative agents.