Morris C L, Gruppo R A, Shukla R, Rucknagel D L
Comprehensive Sickle Cell Center, Childrens Hospital Medical Center, Cincinnati OH 45229.
J Lab Clin Med. 1991 Oct;118(4):332-42.
Yield stress is a sensitive index of blood fluidity at low shear stress. Using a method that measured the stress required to cause motion of a thin sedimenting layer of red cells, we found significant elevations of yield stress in patients with homozygous sickle cell anemia during clinical steady state. Mixing studies of sickle cells in normal plasma and buffered saline and of normal red cells in sickle plasma showed (1) that the increased yield stress of sickle blood was not due to differences between sickle and normal plasma factors and (2) that yield stress of sickle cells was not increased in the absence of plasma proteins. Multivariate regression analysis was performed to determine the dependence of sickle blood yield stress on several red cell and plasma factors. The yield stress measurements were normalized for differences in plasma fibrinogen concentration. Other factors studied included cell density, fetal hemoglobin concentration, alpha globin genotype, cell deformability as measured by high shear viscosity, and fibronectin and von Willebrand factor concentrations. Cell density was the primary determinant of yield stress. Measurements of yield stress on density fractionated sickle cells confirmed that the increased yield stress of sickle blood was due to the dense sickle erythrocyte. We conclude that the increased yield stress of sickle blood during clinical steady state was due to an abnormal interaction between the dense sickle cell membrane and plasma protein(s).
屈服应力是低剪切应力下血液流动性的一个敏感指标。使用一种测量使红细胞薄沉降层运动所需应力的方法，我们发现在临床稳定状态下，纯合子镰状细胞贫血患者的屈服应力显著升高。对镰状细胞在正常血浆和缓冲盐溶液中的混合研究以及正常红细胞在镰状血浆中的混合研究表明：（1）镰状血液屈服应力的增加并非由于镰状细胞与正常血浆因子之间的差异；（2）在没有血浆蛋白的情况下，镰状细胞的屈服应力并未增加。进行多变量回归分析以确定镰状血液屈服应力对几种红细胞和血浆因子的依赖性。对血浆纤维蛋白原浓度的差异进行了屈服应力测量的标准化。研究的其他因素包括细胞密度、胎儿血红蛋白浓度、α珠蛋白基因型、通过高剪切粘度测量的细胞变形性以及纤连蛋白和血管性血友病因子浓度。细胞密度是屈服应力的主要决定因素。对密度分级的镰状细胞的屈服应力测量证实，镰状血液屈服应力的增加是由于致密的镰状红细胞所致。我们得出结论，临床稳定状态下镰状血液屈服应力的增加是由于致密的镰状细胞膜与血浆蛋白之间的异常相互作用。
