Tsan M F, Berlin R D
J Exp Med. 1971 Oct 1;134(4):1016-35. doi: 10.1084/jem.134.4.1016.
The activities of specific transport systems were determined before and after large portions of the surface membrane had been interiorized by phagocytosis of inert particles. In five separate transport systems in rabbit polymorphonuclear leukocytes (adenosine and two adenine transport systems) and alveolar macrophages (adenosine and lysine transport systems), the rate of transport was unaffected even after an estimated 35-50% of the membrane had been internalized. Studies of the kinetics of lysine and adenosine transport, exchange diffusion of lysine transport in alveolar macrophages, and the specificities of adenine transport in polymorphonuclear leukocytes indicate that the nature of the membrane transport systems is not altered by phagocytosis. Therefore the constancy of transport indicates that the number of carriers remains the same before and after phagocytosis. It was also shown that this constancy of transport did not depend on the introduction into the surface of new transport sites during phagocytosis. Therefore transport sites are preserved on the surface during the internalization of membrane which accompanies phagocytosis. The results are best explained by the concept that the membrane is mosaic in character with geographically separate transport and phagocytic sites.
在通过吞噬惰性颗粒使大部分表面膜内化之前和之后，测定了特定转运系统的活性。在兔多形核白细胞（腺苷和两个腺嘌呤转运系统）和肺泡巨噬细胞（腺苷和赖氨酸转运系统）的五个独立转运系统中，即使估计有35%-50%的膜已被内化，转运速率仍未受影响。对赖氨酸和腺苷转运动力学、肺泡巨噬细胞中赖氨酸转运的交换扩散以及多形核白细胞中腺嘌呤转运特异性的研究表明，膜转运系统的性质不会因吞噬作用而改变。因此，转运的恒定性表明吞噬前后载体数量保持不变。还表明，这种转运的恒定性并不取决于吞噬过程中在表面引入新的转运位点。因此，在伴随吞噬作用的膜内化过程中，转运位点保留在表面。这些结果最好用这样的概念来解释，即膜具有镶嵌性，在地理上有分开的转运和吞噬位点。
