Removal of small proteins--the stepchild of dialysis therapy. Protein permeability of different hemofiltration membranes analysed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE).

The kidney plays an essential role in the catabolism of small circulating proteins. Low molecular weight proteins (LMWP) with sizes smaller than that of albumin are filtered by the glomerulum and hydrolyzed in the proximal tubular cells after endocytotic absorption1,2,3. Daily filtered LMWP loads are in the range of 5 g. The renal catabolism is responsible for 30 – 80% of the plasma turnover of LMWP1. In renal failure this catabolism is decreased leading to increased LMWP plasma levels, which might contribute to the development of the uremic syndrome as many of the LMWP are biologically active components like enzymes or hormones.