EFFECT OF SULFATED XYLANS ON COAGULATION OF HUMAN PLASMA

注射肝素进行抗凝治疗，这是一种自然发生的 糖胺多聚糖被广泛用于预防肺血栓或 术后深静脉血栓形成。由于商业中的异质性 肝素及其副作用，如出血、血小板减少症 骨质疏松症已经尝试寻找新的抗凝血剂。 聚戊聚糖聚硫酸酯，聚硫化木聚糖钠盐(SP-54) 由慕尼黑Benechemie销售，西德目前在欧洲被用作 肝素的替代品。这种化合物不如肝素有效 其作用机制仍不清楚。我们实验室里的研究 已证明通过对分离的木聚糖进行硫酸盐化而制备的木聚糖硫酸酯 来自植物的材料在体内和体内都是有效的抗凝血剂 体外培养。这些化合物的LD_(50)‘S与肝素相似，为 比有效剂量高出数百倍，表明 临床应用的安全性。这项建议涉及对 硫化木聚糖的抗凝作用机理包括 1)抗凝血酶III(AT-III)-凝血酶动力学分析 或肝素辅因子II(HC-II)与凝血酶的相互作用 硫化木聚糖的存在。2)结合常数的测定 硫酸化木聚糖与AT-III相互作用的研究 关键色氨酸残基微扰引起的荧光增强 AT-III或通过增强芳香族化合物的特定条带 AT-III近紫外圆二色(CD)光谱中的氨基酸 区域。3)~(125)I-凝血酶与AT-III或HC-的络合作用研究 II在硫酸木聚糖存在的情况下，使用体外人血浆。4)A 木聚糖硫酸酯在正常人体内的抗凝性能比较 血浆VS AT-III耗尽血浆。5)约束性的确定 木聚糖硫酸酯与AT-III、凝血酶或HC-II结合的蛋白质位点 改性剂。拟议的研究将使我们深入了解 硫酸化木聚糖改变凝血的机制并可能导致 一种选择性抗凝剂的开发。

Anticoagulant therapy by injection of heparin, a naturally occurring glycosaminoglycan is widely used to prevent pulmonary emboli or postoperative deep vein thrombosis. Due to heterogeneity in commercial heparins and its adverse side effects such as bleeding, thrombocytopenia and osteoporosis attempts have been made to find new antithrombic agents. A pentosan polysulfate, a sodium salt of polysulfated xylan (SP-54) marketed by Benechemie, Munich, West Germany is currently used in Europe as a replacement for heparin. This compound is not as effective as heparin and its mechanism of action remains obscure. Studies in our laboratory have shown that xylan sulfates prepared by sulfation of xylans isolated from plant materials are effective anticoagulants both in vivo and in vitro. The LD50's of these compounds were similar to heparin and were hundred fold higher than the effective dosage suggesting a wide margin of safety in clinical application. This proposal is concerned with studies on the mechanism of anticoagulant action of sulfated xylans and will include the following: 1) Kinetic analysis of antithrombin III (AT-III)-thrombin or heparin cofactor II (HC-II)-thrombin interactions in absence of or in the presence of sulfated xylans. 2) Determination of binding constants for the interactions of sulfated xylans with AT-III by studying the fluorescence enhancement due to perturbation of key tryptophan residue of AT-III or by following the enhancement of specific bands of the aromatic amino acids in the circular dichroism (CD) spectra of AT-III in the near-UV region. 3) Studies of the complexation of 125I-thrombin with AT-III or HC- II in presence of sulfated xylans using ex-in vivo human plasma. 4) A comparison of anticoagulant properties of xylan sulfates in control human plasma versus AT-III depleted plasma. 5) Determination of the binding sites of xylan sulfates with AT-iii, thrombin or HC-II using protein modification reagents. The proposed study will give an insight into the mechanism by which sulfated xylans modify coagulation and may lead to the development of a selective anticoagulant.