on a paper I found that authors evaluated, by spectrofotometric methods, the activity of superoxide dismutase and catalase in brain homogenate, unfortunately brain tissues had been previously treated with formaldehyde 4% for 24h.
to my opinion this is not correct
Formaldehyde diffuses very interior of the cell and make cross-links with proteins. In my opinion, one can't get rid of these cross-links even studying with brain crude homogenates.
In case someone claiming to have an activity of catalase or SOD in these tissue homogenates, they have to be compared with other fomaldehyde treated tissue enzyme activities.
To see what happens when the tissue fixed with formaldehyde in any percent:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3519217/
In my opinion this is not possible, because of the formaldehyde can affect the protein and consequently the catalytic activity. I not fully recommended this procedure.
Dear Marco
I am agree with Guvenc , as formaldehyde makes hard cross-links with tissue proteins, and minding the enzymes-base protocol for SOD you will not succeed to assay the changes.
Good luck
Formaldehyde is a potent fixative and disinfectant. It is capable of inhibiting the activities of bioactive compounds and preserve these compounds in cells and tissues. Intracellular enzymes get fixed in the presence of formaldehyde. Any tissue preserved in 4% formaldehyde may loose their anti-oxidant enzyme activities. Therefore, in my opinion, antioxidant enzyme activities cant not be assayed after 24h of incubation in 4% formaldehyde.
Dear Marco Malaguti,
I totally agree with you. Formaldehyde is a well known fixative, and hence enzyme activity study on formalin fixed tissues is not advisable.
i do agree that this protocol has some discrepancies but however is it not that formaldehyde could store up the enzymes, like keep it in a state whereby the level of the enzymes can then be measured by assays that give antioxidant end products?
Hi! I too agree with all the other Scientists that it is not possible to estimate any anti-oxidant enzyme activities. It is always good to use fresh tissue to estimate any enzyme levels in tissue homogenates.
You have to estimate the enzymes levels in fresh tissue homogenates because formaldehyde fixed the tissues.I agree with all answers that is not possible to measured the enzymes activities in fixed tissues.
So given that the samples are fixed in paraformaldehyde, what protein markers can be measured for oxidative stress/reactive oxygen species? Without using any oxidative stress assay, if the only option is to do either western blotting or qPCR?