MORPHOLOGIC AND BIOCHEMICAL FEATURES AFFECTING THE ANTITHROMBOTIC PROPERTIES OF THE INFERIOR VENA-CAVA OF RABBIT PUPS AND ADULT-RABBITS

The incidence of venous thromboembolic disease is reduced in children compared with adults. Thromboprotective mechanisms, some of which have already been identified in plasma, must be present in children. Blood vessel walls have important antithrombotic properties that maintain b lood fluidity. This is in part due to proteoglycan (PG)-related glycos aminoglycan (GAG) molecules within vessel walls. PGs are macromolecule s with covalently attached GAG chains, either chondroitin, dermatan, h eparan, or keratan sulfate. The influence of age on the concentration and anticoagulant activities of PGs and GAGs, within vein walls before puberty has not been previously investigated. We hypothesized that de velopmental differences in vein walls may contribute to the reduced ri sk of thrombosis in children. We used a rabbit model to examine morpho logic and biochemical features of inferior venae cavae (IVCs). We asse ssed IVC wall morphology, PG distribution, GAG mass, and GAG antithrom bin activity. Morphologically, there were only minor differences betwe en pups and adult rabbits' IVCs. However, there was a significant incr ease in GAGs by mass in IVCs from pups compared with adult rabbits (p = 0.012). In addition the total antithrombin activity (p = 0.04), and especially that of heparan sulfate (p = 0.01) was significantly increa sed in pups compared with adult rabbits. These results demonstrate imp ortant differences in the antithrombotic properties of NC walls in pup s and adult rabbits. In summary, developmental differences in vein wal l PG content and activity exist which may contribute to the reduced ri sk of venous thromboembolism in children. Further characterization of these differences is required.