Patel J M, Sekharam M, Block E R
Division of Pulmonary Medicine, University of Florida College of Medicine, Gainesville.
Exp Lung Res. 1991 Jul-Aug;17(4):707-23. doi: 10.3109/01902149109062874.
Vitamin E, a dietary antioxidant, is thought to incorporate into the lipid bilayer of biological membranes. We evaluated the lipid composition and distribution of [3H]-vitamin E in various membranes of pulmonary endothelial cells and determined whether vitamin E incorporation caused alterations in membrane structure and function in these cells. Following 6-, 12-, 18-, 24-, and 48-h incubation periods, vitamin E incorporation values were 3.0, 5.7, 6.9, 7.2, and 6.8 nmol/mg protein or 3.8, 7.3, 8.8, 9.2, and 8.7 nmol/mg phospholipid in mitochondrial membranes and 2.0, 4.4, 5.2, 5.3, and 5.0 nmol/mg protein or 3.5, 7.7, 9.1, 9.3, and 8.8 nmol/mg phospholipid in microsomal membranes, respectively. Vitamin E incorporation into the plasma membranes was greater than in mitochondrial and microsomal membranes after 12-, 24-, and 48-h incubations (18.9, 20.8, and 19.6 nmol/mg protein, respectively [P less than .001] versus mitochondria and microsomes or 12.2, 13.4, and 12.6 nmol/mg phospholipid, respectively [P less than .05] versus mitochondria and microsomes). The total phospholipid content, as well as the unsaturation index of the fatty acid content of these membranes, were in the same order, (i.e., plasma membrane greater than mitochondrial membranes and microsomal membranes). The physical state of the intact plasma membrane and the mitochondrial and microsomal membranes were measured by monitoring fluorescence anisotropies (rs) of the molecular probes, diphenylhexatriene (DPH) and trimethylamino-DPH (TMA-DPH). Vitamin E incorporation caused significant increases in rs for DPH (P less than .01) and TMA-DPH (P less than .01) in all three membranes compared to controls. Similar increases in rs values for DPH and TMA-DPH were observed in lipid vesicles prepared from these membranes. Following vitamin E incorporation, 5-hydroxytryptamine (5-HT) transport was measured as an index of plasma membrane function. Vitamin E incorporation resulted in an 18% reduction (P less than .05) in 5-HT uptake. These results indicate that vitamin E was distributed nonuniformly in endothelial cell membranes but resulted in comparable decreases in fluidity in all three membranes. In addition to its role as an antioxidant, vitamin E may alter the membrane physical state and modulate a variety of endothelial cell functions, including 5-HT transport.
维生素E是一种膳食抗氧化剂，被认为可融入生物膜的脂质双层中。我们评估了[3H] - 维生素E在肺内皮细胞各种膜中的脂质组成和分布，并确定维生素E的融入是否会导致这些细胞中膜结构和功能的改变。在6小时、12小时、18小时、24小时和48小时的孵育期后，线粒体膜中维生素E的融入值分别为3.0、5.7、6.9、7.2和6.8 nmol/mg蛋白质或3.8、7.3、8.8、9.2和8.7 nmol/mg磷脂，微粒体膜中分别为2.0、4.4、5.2、5.3和5.0 nmol/mg蛋白质或3.5、7.7,、9.1、9.3和8.8 nmol/mg磷脂。在12小时、24小时和48小时孵育后，质膜中维生素E的融入量大于线粒体膜和微粒体膜（分别为18.9、20.8和19.6 nmol/mg蛋白质[P小于0.001]，与线粒体和微粒体相比；或分别为12.2、13.4和12.6 nmol/mg磷脂[P小于0.05]，与线粒体和微粒体相比）。这些膜的总磷脂含量以及脂肪酸含量的不饱和指数顺序相同，即质膜大于线粒体膜和微粒体膜。通过监测分子探针二苯基己三烯（DPH）和三甲基氨基 - DPH（TMA - DPH）的荧光各向异性（rs）来测量完整质膜以及线粒体和微粒体膜的物理状态。与对照相比，维生素E的融入导致所有三种膜中DPH（P小于0.01）和TMA - DPH（P小于0.01）的rs显著增加。在由这些膜制备的脂质小泡中也观察到DPH和TMA - DPH的rs值有类似增加。维生素E融入后，测量5 - 羟色胺（5 - HT）转运作为质膜功能的指标。维生素E的融入导致5 - HT摄取减少18%（P小于0.05）。这些结果表明，维生素E在内皮细胞膜中分布不均匀，但导致所有三种膜的流动性有相当程度的降低。除了作为抗氧化剂的作用外，维生素E可能会改变膜的物理状态并调节多种内皮细胞功能，包括5 - HT转运。
