Angel A
J Lipid Res. 1970 Sep;11(5):420-32.
The subcellular distribution and composition of endogenously synthesized lipid in isolated white adipose cells were studied to determine the nature and extent of lipid compartmentation. After brief incubation of cells with labeled glucose, acetate, or palmitic acid, over 90% of newly synthesized triglyceride was localized in the bulk-lipid phase, indicating rapid intracellular transport and storage. From 13 to 20% of the newly formed lipid was diglyceride, and over 95% of it was localized in the central lipid-storage vacuole rather than in organelle systems concerned with esterification, thus indicating intracellular segregation of newly synthesized partial glycerides. Most of the newly synthesized phosphatides partitioned with membranous organelles. Synthesis of cholesterol or cholesteryl ester was negligible. After brief incubation of cells with labeled glucose, the relative specific activity of organelle triglyceride was mitochondria >> microsomes > liposomes > soluble supernatant > bulk lipid. In pulse-chase studies the specific activity of organelle triglyceride decreased and that of the bulk fraction increased reflecting intracellular lipid transport. The data suggest that a significant proportion of newly formed lipid is transferred from mitochondrial membranes into the storage vacuole by direct lipid-lipid interaction. Liposomes, which consist of small enclosed lipid droplets resembling chylomicrons, contained triglycerides of specific activity similar to microsomal triglyceride. While the evidence that liposome triglyceride may be microsomal in origin is indirect, the results do indicate that the liposome fraction represents a phase in the transport and(or) storage of new glyceride. At least two forms of compartmentation of newly synthesized lipids occurred. The first, termed "structural," refers to localization of lipids to organelle fractions. The second type of compartmentation, termed "chemical," concerns the intracellular segregation of a specific lipid class. The accumulation and segregation of newly synthesized diglyceride in the bulk storage pool are examples of the latter form of compartmentation.
研究了分离的白色脂肪细胞中内源性合成脂质的亚细胞分布和组成，以确定脂质区室化的性质和程度。在用标记的葡萄糖、乙酸盐或棕榈酸短暂孵育细胞后，超过90%新合成的甘油三酯位于大量脂质相中，表明细胞内快速运输和储存。新形成的脂质中有13%至20%是甘油二酯，其中超过95%位于中央脂质储存液泡中，而不是与酯化有关的细胞器系统中，因此表明新合成的部分甘油酯在细胞内分离。大多数新合成的磷脂与膜性细胞器一起分布。胆固醇或胆固醇酯的合成可以忽略不计。在用标记的葡萄糖短暂孵育细胞后，细胞器甘油三酯的相对比活性为线粒体>>微粒体>脂质体>可溶性上清液>大量脂质。在脉冲追踪研究中，细胞器甘油三酯的比活性下降，而大量部分的比活性增加，反映了细胞内脂质运输。数据表明，相当一部分新形成的脂质通过直接的脂质-脂质相互作用从线粒体膜转移到储存液泡中。脂质体由类似于乳糜微粒的小的封闭脂质滴组成，其甘油三酯的比活性与微粒体甘油三酯相似。虽然脂质体甘油三酯可能起源于微粒体的证据是间接的，但结果确实表明脂质体部分代表了新甘油酯运输和（或）储存的一个阶段。新合成脂质至少有两种区室化形式。第一种称为“结构”，指脂质定位于细胞器部分。第二种区室化类型称为“化学”，涉及特定脂质类别的细胞内分离。新合成的甘油二酯在大量储存池中积累和分离就是后一种区室化形式的例子。
