Plagemann P G, Wohlhueter R M
Biochim Biophys Acta. 1984 Nov 21;778(1):176-84. doi: 10.1016/0005-2736(84)90460-7.
The transmembrane equilibration of radiolabeled uridine was measured by rapid kinetic techniques in human erythrocytes from freshly drawn blood and in the same cells during conventional storage of the blood as well as in cells from outdated blood. Our results confirm earlier reports that the maximum velocity of uridine equilibrium exchange (Vee) at 25 degrees C is about 30% lower in outdated than fresh red cells, whereas the opposite is the case for the Michaelis-Menten constant for equilibrium exchange (Kee), and that maximum zero-trans efflux (Vzt21) is about 4-times greater than maximum zero-trans influx (Vzt12) in outdated cells (directional asymmetry), whereas they are about the same in fresh red cells. At 25 degrees C, the nucleoside-loaded carrier of fresh cells moves on the average 6-times more rapidly than the empty carrier, whereas the differential mobility of loaded and empty carrier from outdated cells is about 15-fold. Our results also show that greater efflux than influx in outdated cells is not due to a general leakiness of outdated cells, that the differences in kinetic properties of the transporter developed during the first two weeks of blood storage and that the differences are greatly amplified when transport is measured at 5 degrees C rather than 25 degrees C. At 5 degrees C, the loaded carrier from outdated red cells moves about 325-times more rapidly than the empty carrier and maximum zero-trans efflux exceeds maximum zero-trans influx about 14-times, whereas the transport of fresh cells exhibits directional symmetry just as at 25 degrees C. The changes in kinetic properties of transport induced by temperature and storage are probably related to structural alterations in the plasma membrane and suggest that the operation of carrier is subject to modification by the membrane environment. Other results show that the kinetics of the sugar transport of human red cells is not affected in the same manner by blood storage as those of the nucleoside transporter.
采用快速动力学技术，测定了取自新鲜血液的人体红细胞、常规储存血液期间的同一细胞以及过期血液中的细胞内放射性标记尿苷的跨膜平衡。我们的结果证实了早期的报道，即25℃时，过期红细胞中尿苷平衡交换的最大速度（Vee）比新鲜红细胞低约30%，而平衡交换的米氏常数（Kee）则相反；过期细胞中的最大零转流外排（Vzt21）比最大零转流内流（Vzt12）大约大4倍（方向不对称），而新鲜红细胞中两者大致相同。在25℃时，新鲜细胞中装载核苷的载体平均移动速度比空载载体快6倍，而过期细胞中装载和空载载体的差异迁移率约为15倍。我们的结果还表明，过期细胞中外排大于内流并非由于过期细胞普遍渗漏所致，转运体的动力学特性差异在血液储存的前两周就已形成，并且当在5℃而非25℃下测量转运时，这些差异会大大放大。在5℃时，过期红细胞中装载的载体移动速度比空载载体快约325倍，最大零转流外排超过最大零转流内流约14倍，而新鲜细胞的转运表现出与25℃时相同的方向对称性。温度和储存引起的转运动力学特性变化可能与质膜结构改变有关，这表明载体的运作会受到膜环境的影响。其他结果表明，人体红细胞糖转运的动力学不像核苷转运体那样受到血液储存的相同影响。
