دانلود رایگان مقاله آنالیز زیست شناسی و ساختاری بخش هپارین گاوی

ABSTRACT

Low molecular weight heparin, which is generally obtained by chemical and enzymatic depolymerization of unfractionated heparin, has high bioavailability and can be subcutaneously injected. The aim of the present investigation was to fractionate bovine heparin using a physical method (ultrafiltration through a 10 kDa cut-off membrane), avoiding structural modifications that can be caused by chemical or enzymatic treatments. Two fractions with different molecular weights were obtained: the first had an intermediate molecular weight (B-IMWH; Mn = 9587 Da) and the other had a high molecular weight (B-HMWH; 22,396 Da). B-IMWH and B-HMWH have anticoagulant activity of 103 and 154 IU/mg respectively, which could be inhibited by protamine. Both fractions inhibited -thrombin and factor Xa in vitro and showed antithrombotic effect in vivo. Moreover, ex vivo aPTT assay demonstrated that B-IMWH is absorbed by subcutaneous route. The results showed that ultrafiltration can be used to obtain two bovine heparin fractions, which differ on their molecular weights, structural components, anticoagulant potency, and administration routes.

5. Conclusion

This study showed that: 1) ultrafiltration of bovine heparin can produce a fraction with greater anticoagulant activity (B-HMWH) and another with lower activity (B-IMWH), but that presents effect when subcutaneously injected; 2) B-IMWH and B-HMWH have similar antithrombotic activity in vivo and the anticoagulant effect of both can be neutralized by protamine sulfate; and 3) the bovine heparin fractions with different molecular weights, obtained by ultrafiltration, have native structural differences. Therefore, ultrafiltration could be used to fractionate bovine heparin to give fractions with good clinical applications. This method could probably be used for porcine heparin too. Interestingly, heparin fractions with different molecular weights have native structural differences, which can influence their anticoagulant and antithrombotic properties. More studies are necessary to describe the relationship between the native structures of these heparin fractions and their activities.