Chromatography of selenoproteins in human serum using matrix-bound heparin

Since previous experiments indicated that a major selenoprotein in human serum interacts with heparin, chromatography of serum on matrix-bound heparin was studied. When human serum was applied to heparin-agarose columns, approximately half of the applied selenium was not retained on the columns. Approx. 40% of the selenium could then be eluted either with increasing concentrations of heparin or ammonium acetate. Using a scaled-down version of this procedure, selenoproteins from 0.5 ml serum were separated into the heparin-binding and non-heparin-binding fractions. In an experiment where healthy subjects were given supplements of yeast selenium (200 micrograms/d) for eight weeks, the concentration of selenium in serum was almost doubled and then approached the original concentration 16 weeks after the end of the supplementation. During supplementation, no change in the concentration of heparin-binding selenoproteins was observed, and instead the increase in serum selenium occurred in non-heparin-binding proteins. This suggests that the need for selenium by the heparin-binding proteins was saturated already at the starting serum selenium level (1.0 mumol/l). Since interaction with heparin has been observed also for selenoprotein P isolated from rat plasma, the protein in the heparin-binding fraction, demonstrated in this paper, may be a human analogue to selenoprotein P.