Yeagle P L, Young J E
J Biol Chem. 1986 Jun 25;261(18):8175-81.
The distribution of cholesterol between vesicles of different lipid composition at equilibrium has been determined. Small, sonicated unilamellar vesicles and large unilamellar vesicles were incubated at a defined temperature, and aliquots were then obtained at selected times for analysis. Inclusion of a small amount of phosphatidylserine or phosphatidylinositol in the membrane does not appreciably affect the distribution of cholesterol at equilibrium by these measurements. A membrane in the gel state is a poor acceptor of cholesterol. The length of the hydrocarbon chain on the phospholipid may also play a role. Bovine brain sphingomyelin dramatically slows the kinetics of cholesterol transfer, and the equilibrium distribution of cholesterol among vesicles containing sphingomyelin is therefore not observable in these experiments. Data obtained with vesicles containing phosphatidylethanolamine indicate a preference of cholesterol for vesicles composed of phosphatidylcholine compared to vesicles consisting primarily of phosphatidylethanolamine, at equilibrium. Experiments with a chaotropic agent indicate that the nature of the surface of the phosphatidylethanolamine bilayer, and its hydration, are important factors in the distribution of cholesterol among membranes in which phosphatidylethanolamine is present. These data suggest that membrane lipid content may play a role in the distribution of cholesterol among the membranes of a cell.
已确定了胆固醇在不同脂质组成的囊泡之间达到平衡时的分布情况。将小的、经超声处理的单层囊泡和大的单层囊泡在特定温度下孵育，然后在选定时间取出等分试样进行分析。通过这些测量发现，在膜中加入少量磷脂酰丝氨酸或磷脂酰肌醇对平衡时胆固醇的分布没有明显影响。处于凝胶态的膜是胆固醇的不良受体。磷脂上烃链的长度也可能起作用。牛脑鞘磷脂会显著减慢胆固醇转移的动力学，因此在这些实验中无法观察到胆固醇在含鞘磷脂的囊泡之间的平衡分布。用含磷脂酰乙醇胺的囊泡获得的数据表明，在平衡时，与主要由磷脂酰乙醇胺组成的囊泡相比，胆固醇更倾向于由磷脂酰胆碱组成的囊泡。用一种离液剂进行的实验表明，磷脂酰乙醇胺双层表面的性质及其水合作用是胆固醇在存在磷脂酰乙醇胺的膜之间分布的重要因素。这些数据表明，膜脂质含量可能在细胞内各膜之间胆固醇的分布中起作用。
