Dimitrov O A, Lalchev Z I
Department of Human and Animal Physiology, Sofia University St. Kliment Ohridski, Faculty of Biology, Bulgaria.
J Steroid Biochem Mol Biol. 1998 Jul;66(1-2):55-61. doi: 10.1016/s0960-0760(98)00002-8.
Interactions of estradiol, progesterone, testosterone and cholesterol with dipalmitoylphosphatidylcholine (DPPC) monolayers at the air/water interface using Wilhelmy-Tensiometer were studied by measuring the change of the monolayer surface tension gamma (mN/m). In order to estimate the role of DPPC phase state on the deltagamma effects the experiments were carried out at three temperatures: 37 degrees C, 41.5 degrees C and 47 degrees C, since at 37 degrees C and 47 degrees C the formation of ripple gel Pbeta and liquid-crystalline Lalpha DPPC phases respectively were realized. Surface tension lowering capacity of the individual components at the air/water interface decreases in the order cholesterol>estradiol>progesterone>testosterone. The surface tension decrease of previously formed DPPC monolayer after addition of cholesterol and hormones follows the order cholesterol>>estradiol>progesterone approximately = testosterone. The higher activity of cholesterol and estradiol is interpreted by the existence of hydroxyl group in the steroid A-ring and hydrocarbon chain in the cholesterol structure and the same hydroxyl group in the estradiol, with possible formation of hydrogen bond between this group and the C=O group of the DPPC. It is shown that the existence of C-H chain in the molecular structure is stronger determinant than the OH group regarding the interactions with the DPPC monolayers. The very low capacity of progesterone and testosterone to interact with the DPPC monolayer is explained by the lack of the C-H chain and OH group in their structures. It was shown that the interaction forces of the steroids studied with DPPC monolayers were dependent on the DPPC phase state, being in any conditions stronger in the Lalpha (47 degrees C) than in Pbeta (37 degrees C) phase. At 41.5 degrees C more complex behavior of the components at the monolayers was observed. The obtained results could serve the concept of regulated entry of the steroid sex hormones into the cells with the participation of the lipid membrane components.
使用威尔海姆张力计研究了雌二醇、孕酮、睾酮和胆固醇与空气/水界面处的二棕榈酰磷脂酰胆碱（DPPC）单层之间的相互作用，通过测量单层表面张力γ（mN/m）的变化来进行研究。为了评估DPPC相态对Δγ效应的作用，实验在三个温度下进行：37℃、41.5℃和47℃，因为在37℃和47℃时分别实现了波纹凝胶Pβ相和液晶Lα相DPPC相的形成。空气/水界面处各组分降低表面张力的能力按胆固醇>雌二醇>孕酮>睾酮的顺序降低。添加胆固醇和激素后，先前形成的DPPC单层的表面张力降低顺序为胆固醇>>雌二醇>孕酮≈睾酮。胆固醇和雌二醇较高的活性可通过甾体A环中存在羟基以及胆固醇结构中的烃链和雌二醇中相同的羟基来解释，该基团与DPPC的C=O基团之间可能形成氢键。结果表明，就与DPPC单层的相互作用而言，分子结构中C-H链的存在比OH基团是更强的决定因素。孕酮和睾酮与DPPC单层相互作用的能力非常低，这是由于它们的结构中缺乏C-H链和OH基团。结果表明，所研究的甾体与DPPC单层的相互作用力取决于DPPC相态，在任何条件下，Lα相（47℃）中的相互作用力都比Pβ相（37℃）中的更强。在41.5℃时，观察到单层中各组分的行为更为复杂。所得结果可为甾体性激素在脂质膜成分参与下调节进入细胞的概念提供依据。
