Low molecular mass thiols, disulfides and protein mixed disulfides in rat tissues: Influence of sample manipulation, oxidative stress and ageing

Most of the data in studies investigating the contribution of oxidative stress to some human diseases and to ageing derive from measurements carried out in blood, on the basis of the assumption that any alteration of the hematic thiol/disulfide balance should reflect a corresponding alteration in other less accessible tissues. But it is evident that the information that can be gleaned from a direct analysis in specific tissues is largely greater. Nevertheless, the accurate measurement of disulfides is frequently hampered by the artifactual oxidation occurring during sample manipulation as a consequence of the presence of heme-proteins. Therefore, the levels of disulfide forms of low molecular mass thiols in tissues are still poorly investigated, even if their measurements could represent a powerful index of the oxidative status. Here we have used an artifact-free procedure to measure low molecular mass thiols and their disulfides in different rat tissues. Our findings suggest that disulfides are a reliable biomarker of even slight oxidative damage. In tissues of aged rats we observed that either oxidative stress or glutathione depletion alone can occur in different tissues during ageing. Interestingly, among the investigated thiols, only homocysteine showed a tendency to increase in some organs with ageing.

Research highlights
► Alkylation of thiols prevents their artefactual oxidation during sample manipulation.
► Tissue disulfides are sensitive biomarkers of oxidative stress.
► In aged rats the increase of disulfides in some tissues suggests that oxidative stress occurs.
► In aged rats glutathione decreases in some tissues without the occurrence of oxidative stress.
► In aged rats homocysteine increases in some tissues.