Zicha J, Kunes J, Le Quan Sang K H, Devynck M A
Necker Medical School, CNRS URA 1482, Paris, France.
Life Sci. 1993;52(19):1559-65. doi: 10.1016/0024-3205(93)90056-9.
Our previous experiments in human and rat platelets demonstrated that the absence of extracellular Na+ increased the fluorescence anisotropy of TMA-DPH (trimethylamino-diphenylhexatriene, probe preferentially incorporated into the outer leaflet of the plasma membrane). Here we investigated further the in vitro effects of Na+ ions on membrane dynamic properties. Na(+)-dependent changes were reversible and they required about 10-20 min to be induced. They were specifically located in the TMA-DPH environment because they were not observed with diphenylhexatriene (probe non-selectively incorporated into all hydrophobic domains of the cell). To evaluate the possible influence of the intracellular Na+, the effects of sodium replenishment, monensin, ouabain and thrombin on TMA-DPH anisotropy were measured. A rise in intracellular Na+ above the physiological level was associated with unchanged or slightly decreased TMA-DPH anisotropy whereas its decrease was accompanied by a pronounced rise in TMA-DPH anisotropy. Our data indicate that the changes in intracellular Na+ concentration, rather than those in extracellular Na+ concentration, are responsible for the alterations in platelet membrane fluidity probed by TMA-DPH.
我们之前在人类和大鼠血小板上进行的实验表明，细胞外 Na+ 的缺失会增加 TMA-DPH（三甲基氨基二苯基己三烯，优先掺入质膜外小叶的探针）的荧光各向异性。在此，我们进一步研究了 Na+ 离子对膜动态特性的体外影响。Na+ 依赖性变化是可逆的，诱导这些变化大约需要 10 - 20 分钟。它们特定地位于 TMA-DPH 环境中，因为用二苯基己三烯（非选择性掺入细胞所有疏水结构域的探针）未观察到这些变化。为了评估细胞内 Na+ 的可能影响，测量了钠补充、莫能菌素、哇巴因和凝血酶对 TMA-DPH 各向异性的影响。细胞内 Na+ 升高到生理水平以上与 TMA-DPH 各向异性不变或略有降低相关，而其降低则伴随着 TMA-DPH 各向异性的显著升高。我们的数据表明，细胞内 Na+ 浓度的变化而非细胞外 Na+ 浓度的变化，是导致 TMA-DPH 探测到的血小板膜流动性改变的原因。
