Studies on Fractionated Heparin

Abstract

Commercial porcine heparin has been divided into five different molecular weight components following gel filtration upon a polyacrylamide-agarose gel matrix. Rechromatography has shown that the two extreme fractions, which contain very low and very high molecular weight material, were totally separable upon gel filtration, while the intermediate fractions contained material in common with other fractions. Four of the five fractions contained almost equivalent specific activity when measured by an anti-Factor Xa clotting assay (l) and yet had very different specific activities if assayed by either thrombin clotting time or kaolin-cephalin clotting time methods. The highest MW fraction had low specific activity in all of the clotting assays, suggesting that it contained the greatest percentage of a non-reactive material demonstrated by Rosenberg et al, (2) while the lowest MW fraction had low activity only in thrombin clotting time and KCCT assays. The lowest MW fraction produced a smaller acceleration of purified fibrin monomer polymerisation rate and also smaller inhibition of thrombin induced platelet aggregation in plasma. The demonstration of different results for specific activities of the heparin fractions, depending upon the assay method used is in agreement with a recent study (3) and has important implications in regard to the pharmacopeal assays for heparin. It also suggests that heparins with higher specific anti-Factor Xa (or antithrombotic) effect can be prepared from commercial heparins, although these may have a relatively low ability to neutralise thrombin in plasma.