This review will focus on major methodological aspects related to urine sample collection, storage and analysis by 2D-PAGE and attempt to define an advanced normal urine protein map.
Overall, 1118 spots were reproducibly found in normal urine samples but only 275 were characterized as isoforms of 82 proteins. One-hundred height spots belonging to 30 proteins were also detected in plasma and corresponded to typical plasma components. The identity of most of the proteins found in normal urine by 2D-PAGE remains to be determined, the majority being low-molecular weight proteins (< 30 kDa). Equalization procedures would also enhance sensitivity of the analysis and allow low abundance proteins to be characterized.
Therefore, we are still on the way to define the normal urine composition. Technology advancements in concentrating procedure will improve sensitivity and give the possibility to purify proteins for mass spectrometry.