Plasma protein adsorption to hemodialysis membranes: studies in an in vitro model

Upon interaction of whole blood with foreign materials, heterogeneous protein films are deposited onto the artificial surface (eg, hemodialysis membranes). The composition of these protein films subsequently affects various processes, eg, thrombogenesis or activation of the complement system. We developed an in vitro model with which we can identify and study proteins interacting with capillaries during hemodialysis. Using this model we studied the cuprophane dialyzer GFS 120 (CP) and the polymethylmetacrylate membrane Filtryzer B2-1.2 (PMMA). Heparinized whole blood from healthy young volunteers was dialyzed on an extracorporeal dialysis machine. After the dialysis procedure the adsorbed material was eluted from the hemodialysis membranes by different eluants and subsequently analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. A number of proteins could be identified in the eluates of both membrane types. Interestingly, platelet glycoproteins could only be found in PMMA eluates. Albumin, IgG, and antithrombin III were mainly present in the cuprophane eluates. Fibrinogen was demonstrable in all eluates, but in relatively low amounts, and the protein was significantly degraded. Degradation products of antithrombin III and complement factor 3 could also be identified. The process causing the degradation has not yet been identified, but may be due to proteases released from damaged cells.