Lange Y, Cohen C M, Poznansky M J
Proc Natl Acad Sci U S A. 1977 Apr;74(4):1538-42. doi: 10.1073/pnas.74.4.1538.
We studied the exchange of cholesterol between radioactively labeled plasma and human erythrocytes. Results from experiments in which [3H]cholesterol and [14C]-cholesterol were exchanged sequentially into the cells and back out into unlabeled plasma, showed that transmembrane movement of cholesterol occurred with a half-time that was either less than 50 min or greater than 10 days. To obtain further information about the transmembrane movement of cholesterol, we used a technique [Jacobson, B. S. & Branton, D. (1977) Science 195, 302-304] for exposure of the cytoplasmic surface of erythrocyte membranes. This method involved the ionic attachment of erythrocytes to derivatized glass beads followed by disruption of the cells, leaving the beads covered by membrane with the cytoplasmic surface exposed [3H]Cholesterol was exchanged into intact erythrocytes which then were attached to beads. The beads with attached membrane were incubated with phospholipid-cholesterol vesicles and the exchange of cholesterol between the membrane cytoplasmic surface and vesicles was studied. We found that [3H]cholesterol was present at the cytoplasmic surface, indicating that transmembrane movement of cholesterol had occurred within the 2.5 hr required to complete the experiment. This result suggests that the more rapid rate of transmembrane cholesterol movement, inferred from the experiments described above, is the one that applies.
我们研究了放射性标记血浆与人类红细胞之间胆固醇的交换。在实验中，[3H]胆固醇和[14C]胆固醇依次被交换进入细胞，然后再回到未标记的血浆中，实验结果表明，胆固醇的跨膜运动发生的半衰期要么小于50分钟，要么大于10天。为了获得更多关于胆固醇跨膜运动的信息，我们使用了一种技术[雅各布森，B.S.和布兰顿，D.（1977年）《科学》195，302 - 304]来暴露红细胞膜的细胞质表面。该方法包括将红细胞离子附着在衍生化的玻璃珠上，然后破坏细胞，使珠子被膜覆盖且细胞质表面暴露。[3H]胆固醇被交换到完整的红细胞中，然后将红细胞附着在珠子上。将带有附着膜的珠子与磷脂 - 胆固醇囊泡一起孵育，并研究膜细胞质表面与囊泡之间胆固醇的交换。我们发现[3H]胆固醇存在于细胞质表面，这表明在完成实验所需的2.5小时内发生了胆固醇的跨膜运动。这一结果表明，从上述实验推断出的胆固醇跨膜运动的较快速率是适用的。
