Sune A, Vidal M, Morin P, Sainte-Marie J, Bienvenue A
Laboratoire de Biologie Physico-chimique, UA 530 CNRS, USTL, Montpellier, France.
Biochim Biophys Acta. 1988 Dec 22;946(2):315-27. doi: 10.1016/0005-2736(88)90407-5.
The distribution and transverse diffusion kinetics of four spin-labeled phospholipid analogues (two with choline heads: phosphatidylcholine (PC) and sphingomyelin (SM); two with amino heads: phosphatidylserine (PS) and phosphatidylethanolamine (PE) were studied in the plasma membrane of guinea pig blood cells: erythrocytes, reticulocytes, and leukemic lymphocytes. Nitroxide reduction by the internal content of the cells was used as an indicator to determine the phospholipids that penetrated the cells. The reduction rates were in the order, PS greater than PE greater than PC greater than SM in all cells. Reoxidation of phospholipids extracted by serum albumin revealed the distribution of the phospholipids at a given time. In all cells, the distribution equilibrium was reached in less than 2 h and the amounts left in the external leaflet were in the following proportional order: PS less than PE less than PC less than SM. In the erythrocytes and especially in the reticulocytes, the shape change induced by adding phospholipids relaxed partially or completely at a lower speed but kept the same proportional order as at equilibrium. All the results were analyzed quantitatively with a simple kinetic model including the rates of transverse diffusion (flip and flop), the exchange between plasma membrane and internal membranes, and the reduction rate of free radicals (determined in either the internal or external membrane leaflet). The calculated rate constants of transverse diffusion varied from 2 x 10(-3) to 1.2 x 10(-1) min-1 for the flip and from 4 x 10(-3) to 1.2 x 10(-1) for the flop, depending on the polar head and the cell type. Possible interpretations of the external phospholipid reduction mechanism and cell deformation are discussed.
研究了四种自旋标记磷脂类似物（两种带有胆碱头部：磷脂酰胆碱（PC）和鞘磷脂（SM）；两种带有氨基头部：磷脂酰丝氨酸（PS）和磷脂酰乙醇胺（PE））在豚鼠血细胞（红细胞、网织红细胞和白血病淋巴细胞）质膜中的分布及横向扩散动力学。利用细胞内部成分对氮氧化物的还原作为指标来确定穿透细胞的磷脂。在所有细胞中，还原速率的顺序为PS＞PE＞PC＞SM。血清白蛋白提取的磷脂再氧化揭示了特定时间磷脂的分布情况。在所有细胞中，不到2小时就达到了分布平衡，留在外小叶的磷脂量按以下比例顺序排列：PS＜PE＜PC＜SM。在红细胞尤其是网织红细胞中，添加磷脂诱导的形状变化以较低速度部分或完全松弛，但保持与平衡时相同的比例顺序。所有结果都用一个简单的动力学模型进行了定量分析，该模型包括横向扩散（翻转和摆动）速率、质膜与内膜之间的交换以及自由基的还原速率（在内膜或外膜小叶中测定）。根据极性头部和细胞类型的不同，计算出的横向扩散速率常数，翻转时从2×10⁻³到1.2×10⁻¹ min⁻¹，摆动时从4×10⁻³到1.2×10⁻¹ min⁻¹。讨论了外部磷脂还原机制和细胞变形的可能解释。
