Interaction of human platelets with heparinized agarose gel

Platelet interaction with surfaces to which heparin had been covalently bonded was investigated with a chromatographic technique employing agarose gel beads heparinized via a cyanogen bromide reaction. Heparinization significantly increased platelet retention by the gel. Platelet retention was unchanged after pretreatment of the heparinized gel with albumin but increased after pretreatment with fibrinogen. Pretreatment with plasma or purified AT III decreased platelet retention. Reduction in platelet retention was correlated with the amount of AT III removed from plasma. Plasma with decreased levels of AT III was less effective in surface passivation. Pretreatment of heparinized gel with PF4 or protamine sulfate did not decrease platelet retention, but subsequent exposure to plasma did. The results suggest that a surface with covalently bonded heparin is reactive toward platelets but can be passivated by formation of a heparin/AT III complex.