Serum albumin fragmentation in end-stage renal disease patients - a pilot study

BACKGROUND: The goal of this study was to detect modification in the expression of plasma proteins and/or post-translational modifications of their structure in patients with end stage renal disease. METHODS: Serum samples from 19 adult patients treated by maintenance hemodialysis (MHD) were analyzed in comparison to sera from six healthy controls using sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis (2DE). Spots of interest were identified by mass spectrometry analysis. In addition, the 2DE maps were incubated with a human anti-albumin polyclonal antibody. RESULTS: SDS-PAGE gels, 2DE maps and matrix-assisted laser desorption/ionization time of flight analysis indicated over-expression of low-molecular weight proteins (LMWP) in sera from patients. Unexpectedly, another 15 spots with estimated M(r) of 12.5-29 kDa from the 2DE maps of six patients were identified as fragments of albumin. 2D immunoblotting of sera from 12 other patients detected numerous albumin fragments. CONCLUSIONS: These results indicate that in addition to increased expression of LMWP, a relevant amount of albumin fragments are detectable in the serum of patients undergoing MHD. Uremia appears to facilitate the fragmentation of albumin and/or the retention of albumin fragments in blood.