Disruption of thiol homeostasis in plasma of terminal renal failure patients.

Background: The aim of the present studies was to investigate the changes in concentrations of different forms of thiols in plasma of terminal renal failure patients before and after hemodialysis.

Methods: Total concentrations of thiols, their free forms and the level of their mixed disulfides with proteins were determined with HPLC.

Results: In terminal renal failure patients before dialysis, total concentrations of cysteine, homocysteine and cysteinylglycine and their free and protein-bound fractions increased while level of all such forms of glutathione dropped. A single dialysis session caused short-lasting return of concentrations of all forms of thiols to the level equal or close to the control group. The changes observed in non-dialyzed patients were similar to those observed in dialyzed patients before single dialysis procedure.

Conclusions: The obtained results showed severe disturbance of thiol homeostasis in plasma of terminal renal failure patients. The following changes have to be emphasized: (1) high level of free cysteine (cystine) fraction, (2) strong tendency of homocysteine to form mixed disulfides with proteins, (3) drop of glutathione level. These observations confirm a suggestion that atherogenic action of homocysteine can be a result of S-homocysteinylation and N-homocysteinylation reactions, whereas toxic action of cysteine can result from auto-oxidation reaction.