Johnstone R M, Adam M, Hammond J R, Orr L, Turbide C
J Biol Chem. 1987 Jul 5;262(19):9412-20.
Vesicles are released during the in vitro culture of sheep reticulocytes which can be harvested by centrifugation at 100,000 X g for 90 min. These vesicles contain a number of activities, characteristic of the reticulocyte plasma membrane, which are known to diminish or disappear upon reticulocyte maturation. The activities include acetylcholinesterase, cytochalasin B binding (glucose transporter) nucleoside binding (i.e. nucleoside transporter), Na+-independent amino acid transport, and the transferrin receptor. Enzymes of cytosolic origin are not detectable or are present at low activity in the vesicles. Cultures of whole blood, mature red cells, or white cells do not yield comparable levels of these activities, supporting the conclusion that the activities arise from the reticulocytes. In addition, the lipid composition of the vesicles shows the high sphingomyelin content characteristic of sheep red cell plasma membranes, but not white cell or platelet membranes, also consistent with the conclusion that the vesicles are of reticulocyte origin. It is suggested that vesicle externalization may be a mechanism for shedding of specific membrane functions which are known to diminish during maturation of reticulocytes to erythrocytes.
在绵羊网织红细胞的体外培养过程中会释放出囊泡，这些囊泡可通过在100,000×g离心90分钟进行收集。这些囊泡含有许多网织红细胞质膜特有的活性物质，已知这些活性物质在网织红细胞成熟时会减少或消失。这些活性包括乙酰胆碱酯酶、细胞松弛素B结合（葡萄糖转运蛋白）、核苷结合（即核苷转运蛋白）、不依赖钠离子的氨基酸转运以及转铁蛋白受体。囊泡中未检测到胞质来源的酶，或其活性很低。全血、成熟红细胞或白细胞的培养物不会产生相当水平的这些活性，这支持了这些活性源自网织红细胞的结论。此外，囊泡的脂质组成显示出绵羊红细胞质膜特有的高鞘磷脂含量，但白细胞或血小板膜则没有，这也与囊泡源自网织红细胞的结论一致。有人提出，囊泡外化可能是一种机制，用于去除特定的膜功能，已知这些功能在网织红细胞成熟为红细胞的过程中会减少。
