NATURE OF ANTITHROMBIN ACTIVITY OF INTIMAL EXTRACT FROM BOVINE AORTA

Antithrombin activity of intimal extract from bovine aorta was studied using thrombin-purified fibrinogen system. On DEAE-cellulose chromatography, the antithrombin activity of the extract was separated into two active fractions. Both revealed respectively very weak activities and their developing patterns of the activity, during the incubation period with thrombin, were different from each other and also that of original intimal extract before fractionation with the chromatography. But a mixture of these two fractions revealed a high antithrombin activity and the developing pattern of the activity was similar to that of original intimal extract. One of the active fractions seemed to contain plasma antithrombin, almost certainly heparin cofactor and antithrombin III, and the other contained acid mucopolysaccharides of the intimal wall. The acid mucopolysaccharides isolated from the intimal extract extremely enhanced the action of plasma antithrombin obtained from blood. The acid mucopolysaccharides concerned seemed to consist of heparitin sulfate and chondroitin sulfate B as judged by Dowex 1-X2 chromatography, electrophoretic mobility and enzyme treatments. Heparitin sulfate fraction had stronger function than chondroitin sulfate B fraction to yield the antithrombin activity under our experimental conditions. It seemed most likely that the antithrombin activity of the intimal extract was due to a synergistic action of acid mucopolysaccharides, i.e. heparitin sulfate and chondroitin sulfate B, on the action of plasma antithrombin, i.e. heparin cofactor and antithrombin III which infiltrated into the intimal wall from blood.