Size-selectivity of a synthetic high-flux and a high cut-off dialyzing membrane compared to that of the rat glomerular filtration barrier

Abstract

The aim of the present study was to investigate the size-selectivity of two different synthetic dialyzing membranes, having widely differing sieving properties, with respect to their handling of polydispersed fluorescein isothiocyanate (FITC)-Ficoll, FITC-dextran and of proteins, i.e. 125I-human serum albumin (RISA) and 125I-myoglobin (Myo). Are Ficoll and dextran, compared to proteins, " hyperpermeable" across synthetic dialyzing membranes, similar to their behavior across the glomerular filtration barrier (GFB)? A high-flux membrane (HF-Revaclear ®; n=12) and a high cut-off membrane (HCO; n=14) in capillary mini-dialyzers were perfused with diluted horse serum. The perfusate contained polydisperse FITC-Ficoll 70/400 or FITC-dextran (molradius 13-80Å), FITC-Inulin, and, in some experiments, RISA/Myo. After a priming period, sampling of filtrate occurred, and a midpoint plasma sample taken. Filtrate-to-plasma concentration ratios (θ) vs. molecular radius (a e) were assessed using HPLC for Ficoll and dextran. Size-selectivity for Ficoll increased in the order: HF-Revaclear ®