Kolena J, Kasal A
Institute of Experimental Endocrinology, Slovak Academy of Sciences, Bratislava, Czechoslovakia.
Biochim Biophys Acta. 1989 Mar 13;979(3):279-86. doi: 10.1016/0005-2736(89)90245-9.
Incubation of rat testicular membranes with cholesteryl hemisuccinate resulted in an increase in both membrane lipid microviscosity and 125I-labelled hCG specific binding. The purpose of this investigation was to establish which functional groups of cholesteryl hemisuccinate are important for the stimulatory effects. The data obtained showed that only esters of cholesterol with dicarboxylic acids, not those of monocarboxylic acids, increase the accessibility of LH/hCG receptors and membrane rigidity. Experiments with cholesteryl sulfates showed that there are polar groups on C3 carbon of cholesterol having no stimulatory effect on receptors, although an increase in membrane rigidity occurred. The side-chain of cholesterol is important for the stimulatory action. Androstenolone hemisuccinate was ineffective in this respect. On the other hand, partially modified side-chains (hemisuccinates of beta-sitosterol and stigmasterol) did not result in a marked reduction of the stimulatory action. The carboxyl group of cholesteryl hemisuccinate must be 'free': its esterification abolishes the stimulatory effect of cholesteryl hemisuccinate on both the LH/hCG receptor and membrane microviscosity. These results suggest that an intact carboxyl group of ester and the side-chain of cholesterol are indispensable for the stimulatory effect of cholesteryl hemisuccinate on the accessibility of LH/hCG receptors.
用胆固醇半琥珀酸酯孵育大鼠睾丸膜，导致膜脂质微粘度和125I标记的hCG特异性结合均增加。本研究的目的是确定胆固醇半琥珀酸酯的哪些官能团对刺激作用很重要。获得的数据表明，只有胆固醇与二元羧酸的酯，而不是与一元羧酸的酯，会增加LH/hCG受体的可及性和膜刚性。用胆固醇硫酸盐进行的实验表明，胆固醇C3碳上的极性基团对受体没有刺激作用，尽管膜刚性有所增加。胆固醇的侧链对刺激作用很重要。雄甾烯醇半琥珀酸酯在这方面无效。另一方面，部分修饰的侧链（β-谷甾醇和豆甾醇的半琥珀酸酯）并未导致刺激作用明显降低。胆固醇半琥珀酸酯的羧基必须是“游离的”：其酯化消除了胆固醇半琥珀酸酯对LH/hCG受体和膜微粘度的刺激作用。这些结果表明，酯的完整羧基和胆固醇的侧链对于胆固醇半琥珀酸酯对LH/hCG受体可及性的刺激作用是不可或缺的。
