Linderkamp O, Meiselman H J
Blood. 1982 Jun;59(6):1121-7.
Although there is evidence that the deformability of the entire red blood cell (RBC) decreases during aging, reports on changes in relevant specific properties associated with the aging process are limited and not in total agreement. The purpose of this study was to evaluate some of the factors that might contribute to this decreased deformability. Geometric, osmotic, and membrane mechanical properties of unfractionated, top ("young") and bottom ("old") RBC from 5 healthy adult donors were measured using micropipette techniques. Surface area, volume, and diameter of RBC were measured at osmolalities of 297, 254, 202, and 153 mosm/kg. Two membrane mechanical properties, surface shear modulus of elasticity (mu) and time constant (tc) of viscoelastic recovery, were studied only in isotonic media. At each of the osmolalities, volume and surface area of the bottom cells were about 25% lower than those of the top cells. Bottom cells showed smaller increases in volume with decreasing osmolality than top cells; the surface area remained constant with changing osmolality for all three groups. The surface area-to-volume ratio and the minimum cylindrical diameter of the bottom cells were essentially identical to the top cells. However, both the surface area index (actual are of RBC divided by area of a sphere of same volume) and the swelling index (maximal volume divided by actual volume) of the bottom cells were significantly lower than top RBC. The shear modules of elasticity (mu) was about 0.006 dyne/cm in all 3 RBC populations, indicating that the forces necessary to deform a portion of the membrane did not change with RBC aging. The viscoelastic time constant (tc) was 0.148 +/- 0.020 (SD) sec for the bottom RBC and 0.099 +/- 0.017 sec for the top cells. This difference indicates that shape recovery following membrane deformation is delayed in old RBC. The membrane surface viscosity (eta), calculated as the product of tc times mu was 0.95 +/- 0.22 x 10(-3) dyne-sec/cm for the bottom cells and 0.54 +/- 0.15 x 10(-3) for the top RBC. These data indicate that the relative deficit in membrane surface area and the increased membrane viscosity of old RBC may be important determinants for their decreased deformability and their eventual removal from the circulation.
尽管有证据表明，在衰老过程中整个红细胞（RBC）的可变形性会降低，但关于与衰老过程相关的特定属性变化的报道有限，且并未完全达成一致。本研究的目的是评估一些可能导致这种可变形性降低的因素。使用微量移液器技术测量了来自5名健康成年供体的未分级、上层（“年轻”）和下层（“年老”）红细胞的几何、渗透和膜力学特性。在297、254、202和153 mosm/kg的渗透压下测量了红细胞的表面积、体积和直径。仅在等渗介质中研究了两种膜力学特性，即表面剪切弹性模量（μ）和粘弹性恢复的时间常数（tc）。在每个渗透压下，下层细胞的体积和表面积比上层细胞低约25%。随着渗透压降低，下层细胞体积的增加幅度小于上层细胞；所有三组的表面积随渗透压变化保持恒定。下层细胞的表面积与体积之比和最小圆柱直径与上层细胞基本相同。然而，下层细胞的表面积指数（红细胞实际面积除以相同体积球体的面积）和肿胀指数（最大体积除以实际体积）均显著低于上层红细胞。所有3组红细胞群体的剪切弹性模量（μ）约为0.006达因/厘米，表明使膜的一部分变形所需的力不会随红细胞衰老而改变。下层红细胞的粘弹性时间常数（tc）为0.148±0.020（标准差）秒，上层细胞为0.099±0.017秒。这种差异表明，衰老红细胞在膜变形后的形状恢复延迟。通过tc乘以μ计算得出的膜表面粘度（η），下层细胞为0.95±0.22×10⁻³达因·秒/厘米，上层红细胞为0.54±0.15×10⁻³。这些数据表明，衰老红细胞膜表面积的相对不足和膜粘度的增加可能是其可变形性降低以及最终从循环中清除的重要决定因素。
