PRESENCE OF CONTRACTILE PROTEINS IN PLATELET MICROPARTICLES ISOLATED FROM HUMAN AND ANIMAL PLATELET-FREE PLASMA
PRESENCE OF CONTRACTILE PROTEINS IN PLATELET MICROPARTICLES ISOLATED FROM HUMAN AND ANIMAL PLATELET-FREE PLASMA
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DOI：
10.1111/j.1365-2141.1971.tb03416.x
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发表时间：
1971-01-01
影响因子：
6.5
通讯作者：
CRAWFORD, N
中科院分区：
文献类型：
--
作者：
CRAWFORD, N
摘要：通过稀释血浆以降低比重，然后高速超速离心，从人和动物的无血小板血浆中制备了微粒。测定了这些微粒的蛋白质、胆固醇和磷脂含量(以及胆固醇-磷脂比率)，并与全血小板匀浆和各种分离的血小板亚细胞部分的数值进行了比较。对血小板匀浆的微粒和密度梯度组分的免疫学研究表明，这些微粒可能起源于血小板的表面膜或细胞内膜结构。微粒具有相关的ATP酶活性，虽然比活性低于分离的血小板‘收缩蛋白’(凝血酶)，但对二价阳离子、山梨醇和哇巴因的反应具有相似的特征。凝血酶抗血清和抗凝血酶微粒的抗血清均能在较高稀释度下抑制凝血玻璃体缩回素，也能抑制血小板匀浆和血小板凝血酶的镁-三磷酸腺苷酶活性。当检测来自蔗糖密度梯度的血小板亚细胞部分时，这两种抗血清都显示出对低密度膜部分的沉淀抗体。这一组分几乎全部由小的囊泡和较大的片状膜碎片组成。在超微结构上，这些微粒类似于存在于薄壁囊内部的细小颗粒物，这在从新鲜血小板制备的电子显微镜中经常可以看到。这些囊被认为是伪足萌发或细胞质内容物突出穿过血小板壁的结果。
Summary.Microparticles have been prepared from human and animal plateletfree plasma by dilution of the plasma to lower the specific gravity followed by high‐speed ultracentrifugation. The protein, cholesterol, and phospholipid content (and cholesterol‐phospholipid ratios) of these microparticles have been determined and compared with values obtained with whole platelet homogenates and various isolated platelet subcellular fractions. Immunological investigations on the microparticles and on the density gradient fractions of platelet homogenates suggest that the particles may have their origin either in the surface membrane or within the intracellular membrane structures of the blood platelets. The microparticles have an associated ATP‐ase activity which, though lower in specific activity than isolated platelet ‘contractile protein’ (thrombosthenin), has similar characteristics in response to divalent cations, mersalyl and ouabain. Thrombosthenin antisera and antisera to the microparticles both inhibit clot retractionin vitroat high dilution and also inhibit the Mg2+ATP‐ase activity of platelet homogenates and platelet thrombosthenin. When tested against platelet subcellular fractions from sucrose density gradients both these antisera showed precipitating antibodies to the low density membrane fraction. This fraction consists almost entirely of small vesiculated and larger sheet membrane fragments. In ultrastructure, the microparticles resemble the fine granular material present in the interior of thin‐walled sacs which may often be seen in electron‐micrographs prepared from fresh platelets. These sacs are believed to be the result of either budding of the pseudopodia or herniation of the cytoplasmic contents through the platelet wall.