Bernasconi A M, Garda H A, Brenner R R
Instituto de Investigaciones Bioquímicas de La Plata, CONICET-UNLP, Facultad de Ciencias Médicas, Argentina.
Lipids. 2000 Dec;35(12):1335-44. doi: 10.1007/s11745-000-0650-7.
After 21 days on a diet containing 1 g% cholesterol and 0.5 g% cholic acid, rats had an increased content of cholesterol in liver microsomal lipids. In liver, both cholesterol content and delta9 desaturase activity increased, whereas delta6 and delta5 desaturase activities decreased. These changes correlated with increases in oleic, palmitoleic, and linoleic acids and decreases in arachidonic and docosahexenoic acids in total microsomal lipids. Similar fatty acid changes were found in phosphatidylcholine (PC), the principal lipid of the microsomal membrane. In PC the predominant molecular fatty acid species (67% of the total) in the control rats were 18:0/20:4, 16:0/20:4, and 16:0/18:2; and they mainly determined the contribution of PC to the biophysical and biochemical properties of the phospholipid bilayer. The cholesterol diet decreased specifically the 18:0/20:4 species, and to a lesser extent, 16:0/20:4 and 18:0/22:6. The 18:1-containing species, especially 18:1/18:2 and less so 16:0/18:1 and 18:1/20:4, were increased. A new 18:1/18:1 species appeared. The independent effects of the presence of cholesterol and change of the fatty acid composition of the phospholipid bilayer of liver microsomes on the packing were studied by fluorescence methods using 6-lauroyl-2,4-dimethylaminonaphthalene, 1,6-diphenyl-1,3,5-hexatriene and 1-(4-trimethylammonium phenyl)-6-phenyl-1,3,5-hexatriene, which test different parameters and depths of the bilayer. Data showed that the increase of cholesterol in the membrane, and not the change of the fatty acid composition of phospholipids, was the main determinant of the increased bulk packing of the bilayer. The increase of fluid oleic- and linoleic-containing species almost compensated for the drop in 20:4- and 22:6-containing molecules. But the most important effect was that the general drop in essential n-6 and n-3 polyunsaturated fatty acids meant that this endogenous source for the needs of the animal decreased.
在食用含1%胆固醇和0.5%胆酸的饲料21天后，大鼠肝脏微粒体脂质中的胆固醇含量增加。在肝脏中，胆固醇含量和Δ9去饱和酶活性均增加，而Δ6和Δ5去饱和酶活性降低。这些变化与总微粒体脂质中油酸、棕榈油酸和亚油酸的增加以及花生四烯酸和二十二碳六烯酸的减少相关。在微粒体膜的主要脂质磷脂酰胆碱（PC）中也发现了类似的脂肪酸变化。在对照大鼠中，PC中主要的分子脂肪酸种类（占总量的67%）为18:0/20:4、16:0/20:4和16:0/18:2；它们主要决定了PC对磷脂双层生物物理和生化特性的贡献。胆固醇饮食特异性地降低了18:0/20:4种类，在较小程度上降低了16:0/20:4和18:0/22:6。含18:1的种类，特别是18:1/18:2，以及程度稍低的16:0/18:1和18:1/20:4增加。出现了一种新的18:1/18:1种类。使用6-月桂酰-2,4-二甲基氨基萘、1,6-二苯基-1,3,5-己三烯和1-(4-三甲基铵苯基)-6-苯基-1,3,5-己三烯通过荧光方法研究了胆固醇的存在以及肝脏微粒体磷脂双层脂肪酸组成变化对堆积的独立影响，这些物质可检测双层的不同参数和深度。数据表明，膜中胆固醇的增加而非磷脂脂肪酸组成的变化是双层堆积增加的主要决定因素。含流体油酸和亚油酸种类的增加几乎弥补了含20:4和22:6分子的减少。但最重要的影响是必需的n-6和n-3多不饱和脂肪酸普遍减少意味着动物所需的这种内源性来源减少。
