Isoenzyme profile of glutathione S-transferases in human kidney.

Novel glutathione S-transferase (GST) isoenzymes, which do not bind to the glutathione (GSH) affinity column, were recently identified in dog kidney and dog renal cell lines. In humans, similar affinity flow-through GST has been previously found only in the urinary bladder. To ascertain whether these affinity flow-through GST isoenzymes also exist in the human kidney, we separated GST isoenzymes from five kidney samples on the basis of their affinity to GSH affinity resin. GSTs were further purified by anion exchange chromatography and chromatofocusing and characterized with specific substrates. Our results show that the human kidney has both affinity flow-through GST isoenzymes and those which bind tightly to the GSH affinity column. Purification of affinity-bound GST resulted in a rich profile of different isoenzymes with balanced expression of both anionic and cationic forms. Affinity flow-through GST was represented by one isoenzyme (pI-7.9) in all kidney samples tested, but one kidney specimen also contained another GST isoenzyme (pI-7.0). Our results for the first time show the presence of GST isoenzymes that do not bind to GSH-affinity resin in the human kidney. Although the assessment of similarity between the human kidney and urinary bladder affinity flow-through GST requires further elucidation, it can be speculated that these particular GSTs may play an important role in providing protection against the common carcinogens.

Alteration in plasma antioxidant capacity in various degrees of chronic renal failure.

AIM, PATIENTS AND METHODS: To obtain a more comprehensive profile of extracellular antioxidant capacity in chronic renal failure (CRF), markers of oxidative stress (malondialdehyde, MDA and hydrogen peroxide), protein SH groups (as an important chain-breaking antioxidant) and activity of antioxidant enzymes (glutathione peroxidase, [GPX], catalase and superoxide dismutase, [SOD]) were studied in plasma of 36 non-dialyzed patients with various degrees of CRF and 10 hemodialyzed (HD) patients. RESULTS: The results show that plasma MDA concentrations significantly increase with the severity of kidney dysfunction (r = -0.543, p < 0.01). A marked and profound fall in plasma thiol group levels was observed in all groups tested, independent of the degree of renal failure (r = 0.082, p > 0.05). Plasma SOD activity increased in CRF patients with the progression of renal insufficiency (r = -0.370, p < 0.05). On the other hand, plasma GPX activity decreased progressively in strong correlation with endogenous CCr (r = 0.712, p < 0.001). However, despite this imbalance between extracellular SOD and GPX activities, plasma concentration of hydrogen peroxide remained unchanged in non-dialyzed CRF patients. Catalase activity in non-dialyzed CRF patients was increased, suggesting the significant involvement of catalase in the regulation of plasma hydrogen peroxide level. CONCLUSION: In hemodialyzed patients significantly lower plasma catalase activity, associated with higher hydrogen peroxide levels, was found. It seems reasonable to assume that the imbalance in the activity of extracellular antioxidant enzymes in chronic renal failure may result in accumulation of free radical species, and in unscheduled oxidation of susceptible molecules.

Markers of oxidative stress after renal transplantation.

An increased degree of oxidative stress (OS) in chronic renal failure (CRF) and a possible role of free radicals in CRF have already been described. However, data on OS after renal transplantation are scarce. The aim of the present study was to estimate the degree of OS in renal transplant patients. The study included four groups: 1) 15 haemodialysis patients (HD group), 2) 11 renal transplant patients with stable function (SF group), 3) 12 renal transplant patients with chronic biopsy-proven rejection (CR group), and 4) 10 healthy controls (C group). Markers of OS (malondialdehyde and thiol group levels) and antioxidant activity (glutathione peroxidase and Cu,Zn-superoxide dismutase) were determined in plasma and in red blood cells of all examined individuals. After successful renal transplantation a significant improvement, but not normalization, of antioxidant enzyme activities accompanied by significantly reduced lipid peroxidation were found. In the CR group the degree of OS was increased, and our results suggest that OS may be a relevant pathophysiological factor for CR development.