Oxidative stress evaluation in uraemic patients undergoing continuous ambulatory peritoneal dialysis

Since the great bulk of evidences regarding oxidative stress associated with chronic renal failure (CRF) came from haemodialysis patients and only scant data is available concerning peritoneal dialysis, we investigated the oxidative status in CRF patients on continuous ambulatory peritoneal dialysis (CAPD). Plasma lipid peroxidation assayed as thiobarbituric acid reactive substances (TBARS; nmol/g protein), plasma total free thiols (Pt-SH; mcmol/g protein) as marker of extracellular antioxidant status and parameters of enzymatic/non-enzymatic intracellular antioxidant defence (erythrocyte superoxide dismutase (SOD; U/g haemoglobin), glutathione peroxidase (EGPx; U/g haemoglobin) and nonprotein thiols (E-SH; mcmol/g haemoglobin)] were measured by spectrophotometry in 18 CAPD patients, 16 non-dialysed CRF patients and 12 healthy subjects. Increased TBARS were found only in CAPD patients versus Controls (58.3±19.8 vs. 42.7±12.4, p= 0.01). Also, they had lower activity of erythrocyte SOD (164.2±47.5 vs. 463.2±77.5 in CRF group, p<0.001 and 409.8±58.8 in Controls, p<0.001). Plasma thiols were decreased (6.3±0.9 in CAPD group, p=0.03 and 6.1±1.0 in CRF group, p=0.02 vs. 7.2±1.1), while EGPx and E-SH showed gradually elevated values in patients, with the bigger increment in CAPD group (EGPx: 3.3±0.9 in Controls, 4.5±1.3 in CRF group, p=0.01, and 7.9±0.9 in CAPD group, p<0.001; E-SH: 3.2±0.9 in Controls, 4.8±2.5 in CRF group, p= 0.04, and 11.8±1.8 in CAPD group, p<0.001). CAPD patients seem exposed to oxidative stress, evidenced by both an increase in plasma lipid peroxidation and a suppressed activity of antioxidants (SOD, Pt-SH). The enhancement of erythrocyte glutathione-dependent antioxidants, as an adaptive response to oxidative processes, indirectly argues in favour of oxidative stress occurring before initiation of dialysis and augmented thereafter.