Crandall E D, Critz A M, Osher A S, Keljo D J, Forster R E
Am J Physiol. 1978 Nov;235(5):C269-78. doi: 10.1152/ajpcell.1978.235.5.C269.
Fresh human blood was diluted 1:5000 in buffered saline-sucrose solution and titrated to a pH varying from 4.5 to 10.5 with 0.1 N HCl or 0.1 N NaOH. Circular regions of the membrane of individual cells were then deformed at 25 degrees C by aspiration into a micropipette having an internal tip diameter of 0.9-1.4 micron. A membrane surface elasticity modulus, mu (dyn/cm), was computed from the relationship between length of the aspirated membrane and the deforming pressure according to a two-dimensional membrane model. Surface elasticity increases with decreasing pH and with time after the cell suspension is acidified, rising several orders of magnitude with a t1/2 of 1--5 h as pH is lowered from 7.2 to 4.6. This increase in mu is only partially reversible. pH greater than 7.2 had little effect on mu. Membrane surface elasticity is not affected by variations in external [Ca2+] over the range of 0--50 mM, tonicity of the suspension medium from 275--400 mosM, or age of 0--50 h. Addition of 50 mM NaHCO3 to the medium increases the rate of change of mu at a given pH. These results suggest that the elastic properties of the red cell membrane are largely determined by interactions among structural proteins located on the cytoplasmic surface of the membrane and that these interactions are initiated by changes in intracellular pH.
将新鲜人血在缓冲盐水 - 蔗糖溶液中按1:5000稀释，并用0.1N HCl或0.1N NaOH滴定至pH值在4.5至10.5之间变化。然后在25℃下，通过吸入内径为0.9 - 1.4微米的微量移液器使单个细胞的膜的圆形区域变形。根据二维膜模型，由吸出膜的长度与变形压力之间的关系计算膜表面弹性模量μ（达因/厘米）。表面弹性随着pH值降低以及细胞悬液酸化后的时间而增加，当pH值从7.2降至4.6时，μ升高几个数量级，t1/2为1 - 5小时。这种μ的增加只是部分可逆的。pH大于7.2对μ影响很小。在0 - 50mM范围内的外部[Ca2 +]变化、悬浮介质渗透压在275 - 400mosM之间的变化或0 - 50小时的细胞年龄，均不影响膜表面弹性。向培养基中添加50mM NaHCO3会增加在给定pH值下μ的变化速率。这些结果表明，红细胞膜的弹性特性在很大程度上由位于膜细胞质表面的结构蛋白之间的相互作用决定，并且这些相互作用由细胞内pH值的变化引发。
