Blanchette-Mackie E J, Briggs T, Chernick S S, Scow R O
Cell Tissue Res. 1986;244(1):95-105. doi: 10.1007/BF00218386.
Cultured mouse (J774.1) macrophages accumulated triacylglycerol, but no cholesteryl ester or cholesterol, when incubated in albumin-poor medium with serum-activated lipid particles containing 84 mol% trioleoylglycerol and 9 mol% cholesteryl oleate. Accumulation of triacylglycerol by cells was associated with hydrolysis of particulate triacylglycerol to fatty acid and glycerol. Both acyl and glyceryl moieties of particulate triacylglycerol were recovered in cellular triacylglycerol with a molar ratio of 3.6. The cells also accumulated fatty acid and monoacylglycerol. Whether acylglycerol was taken up as a single molecular species, such as monoacylglycerol, or as several species can not be determined by the present findings. Macrophages incubated with lipid particles for 24 h had many lipid particles attached to cell surfaces and numerous intracellular lipid droplets. The surface film of attached particles was continuous with the outer leaflet of plasma membrane of the cells. Particles partially depleted of core triacylglycerol and collapsed surface films were found attached to surfaces of macrophages. There was no morphological evidence that lipid particles were taken up intact by cells, through endocytosis or phagocytosis. Macrophages incubated with lipid particles also contained intracellular lamellar structures. They varied in size and shape, and were located in the periphery of cells, sometimes near lipid droplets and endoplasmic reticulum. Only 3% of the lamellar structures were associated with lysosomes, indicating they probably were not of lysosomal origin. Lipid particles attached to cells decreased in size and number, and lamellar structures developed at the surface of particles, or replaced the particles, when glutaraldehyde-fixed specimens were incubated at 25 degrees C, demonstrating lipolytic activity at the surface of macrophages. Our findings suggest that particulate triacylglycerol was hydrolyzed by lipoprotein lipase at the surface of macrophages, and that fatty acid and monoacylglycerol formed by lipolysis were transported directly into the cells to be reesterified. When lipolytic products were taken up faster than they could be utilized, they accumulated as lamellar structures in the cells.
在含有84摩尔%三油酰甘油和9摩尔%胆固醇油酸酯的血清激活脂质颗粒的白蛋白缺乏培养基中孵育时，培养的小鼠（J774.1）巨噬细胞积累了三酰甘油，但没有胆固醇酯或胆固醇。细胞对三酰甘油的积累与颗粒状三酰甘油水解为脂肪酸和甘油有关。颗粒状三酰甘油的酰基和甘油部分以3.6的摩尔比在细胞三酰甘油中回收。细胞还积累了脂肪酸和单酰甘油。目前的研究结果无法确定酰基甘油是作为单一分子物种（如单酰甘油）还是作为几种物种被摄取。用脂质颗粒孵育24小时的巨噬细胞有许多脂质颗粒附着在细胞表面，并且有大量的细胞内脂质滴。附着颗粒的表面膜与细胞的质膜外小叶连续。发现部分核心三酰甘油耗尽且表面膜塌陷的颗粒附着在巨噬细胞表面。没有形态学证据表明脂质颗粒通过内吞作用或吞噬作用完整地被细胞摄取。用脂质颗粒孵育的巨噬细胞还含有细胞内板层结构。它们大小和形状各异，位于细胞周边，有时靠近脂质滴和内质网。只有3%的板层结构与溶酶体相关，表明它们可能不是溶酶体起源。当戊二醛固定的标本在25℃孵育时，附着在细胞上的脂质颗粒大小和数量减少，颗粒表面形成板层结构或取代颗粒，表明巨噬细胞表面存在脂解活性。我们的研究结果表明，颗粒状三酰甘油在巨噬细胞表面被脂蛋白脂肪酶水解，脂解形成的脂肪酸和单酰甘油直接转运到细胞内进行再酯化。当脂解产物的摄取速度快于其利用速度时，它们在细胞内积累为板层结构。
