de la Maza A, Lopez O, Cocera M, Coderch L, Parra J L
Departamento de Tensioactivos, Consejo Superior de Investigaciones Científicas (C.S.I.C.), Barcelona, Spain.
Chem Phys Lipids. 1998 Aug;94(2):181-91. doi: 10.1016/s0009-3084(98)00051-6.
The role played by the ceramides in the sublytic interactions of sodium dodecyl sulfate (SDS) with liposomes modeling the stratum corneum (SC) lipid composition was studied. The surfactant/lipid molar ratios (Re) and the bilayer/aqueous phase partition coefficients (k) were determined by monitoring the changes in the fluorescence intensity of liposomes due to the 5(6) carboxyfluorescein (CF) released from the interior of vesicles. The presence in liposomes of higher and lower ceramide proportions than that existing in the SC lipids led to a fall and to a rise in the sublytic activity of SDS on these structures. However, the SDS partitioning into liposomes (or affinity with these bilayer structures) increased as the proportion of Cer increased up to achieve almost a constant value for a Cer proportion similar to that in the SC lipids (about 40%). Thus, at low Cer proportions the ability of SDS molecules to alter these bilayer structures was higher than that for liposomes approximating the SC lipid composition despite their reduced partitioning into liposomes. These findings are in agreement with the recently reported dependencies of the level of ceramides in skin lipids and function barrier abnormalities and could explain in part these dependencies. The fact that the free surfactant concentration needed to achieve the two interaction levels investigated was lower than the surfactant critical micellar concentration (CMC) indicates that permeability alterations were mainly ruled by the action of surfactant monomers, regardless of the liposome lipid composition.
研究了神经酰胺在十二烷基硫酸钠（SDS）与模拟角质层（SC）脂质组成的脂质体的亚溶细胞相互作用中所起的作用。通过监测由于从囊泡内部释放的5(6)-羧基荧光素（CF）导致的脂质体荧光强度变化，确定了表面活性剂/脂质摩尔比（Re）和双层/水相分配系数（k）。与存在于SC脂质中的神经酰胺比例相比，脂质体中较高和较低的神经酰胺比例分别导致SDS对这些结构的亚溶细胞活性下降和上升。然而，随着神经酰胺比例增加，SDS在脂质体中的分配（或与这些双层结构的亲和力）增加，直到神经酰胺比例达到与SC脂质中相似的值（约40%）时几乎达到恒定值。因此，在低神经酰胺比例下，尽管SDS在脂质体中的分配减少，但其改变这些双层结构的能力高于接近SC脂质组成的脂质体。这些发现与最近报道的皮肤脂质中神经酰胺水平与功能屏障异常之间的相关性一致，并且可以部分解释这些相关性。达到所研究的两种相互作用水平所需的游离表面活性剂浓度低于表面活性剂临界胶束浓度（CMC），这一事实表明，无论脂质体脂质组成如何，通透性改变主要由表面活性剂单体的作用决定。
