Background: Albumin, the most abundant protein in the extracellular fluid, displays an important antioxidant activity. Increased levels of oxidized albumin levels (high human non-mercaptoalbumin (HNA) level) have been reported in the serum of patients with end-stage renal disease. In this study, we attempted to identify the albumin redox status in the serum of patients on peritoneal dialysis (PD) and examined the relationship between these proteins and the transport type of the peritoneal membrane and other clinical and laboratory variables. Methods: We performed a cross-sectional study of a cohort of 80 patients with end-stage renal disease receiving PD. Peritoneal transport characteristics were identified and after peritoneal equilibration test patients were grouped as high (high(H)/high-average (HA) group, n = 31) or low (low (L)/low-average (LA) group, n = 49) transporters. The redox state of human serum albumin was measured using high-performance liquid chromatography. Results: The fraction of human mercaptoalbumin (HMA) showed significantly higher values in patients with high transport status than those with low transport status (f(HMA) 64.0 ± 5.4 and 52.7 ± 10.4%, respectively). Our data showed that the H/HA transport characteristic was associated with lower albumin (3.76 ± 0.48 vs. 4.00 ± 0.35, p < 0.05), and lower levels of advanced oxidized protein product (p = 0.008) when compared with the L/LA type. A correlation analysis showed that there was a positive correlation between dialysate/plasma (D/P) creatinine and f(HMA) levels (r = 0.511, p < 0.0001), as well as hemoglobin levels r = 0.231, p = 0.044 and a negative correlation between D/P creatinine and serum albumin, cholesterol and LDL levels (r = -0.236, p = 0.039; r = -0.237, p = 0.038; r = -0.272, p = 0.018, respectively). Conclusions: This study showed that higher serum levels of reduced albumin f(HMA) appear to be associated with high/high average peritoneal membrane transport characteristics in the incident PD patients.
