Konikoff F M, Lechene de la Porte P, Laufer H, Domingo N, Lafont H, Gilat T
Department of Gastroenterology, Sourasky Tel-Aviv Medical Center, Tel-Aviv University, Israel.
J Hepatol. 1997 Oct;27(4):707-15. doi: 10.1016/s0168-8278(97)80088-8.
BACKGROUND/AIMS: Cholesterol gallstones contain both calcium and biliary proteins, but their respective roles in gallstone pathogenesis are unknown. We have studied the effects of calcium and a major biliary protein, anionic polypeptide fraction, on the process of cholesterol crystallization in bile.
Anionic polypeptide fraction was purified from human bile. Model bile composed of cholesterol, egg yolk lecithin and sodium taurocholate was prepared in a lipid concentration (18 mM, 37 mM, and 120 mM, respectively) simulating lithogenic human gallbladder bile. The crystallization process was observed by phase contrast light microscopy, and sequential separation of precipitable cholesterol structures by sucrose density gradient ultracentrifugation.
Addition of calcium, or anionic polypeptide fraction alone, or both together did not influence the crystal observation time of bile (the time which elapsed from initiation of supersaturation to the first appearance of crystals). However, the rate and quantity of cholesterol precipitation and crystal formation were affected by both. Calcium increased in a dose-dependent manner the cholesterol monohydrate crystal mass before apparent equilibrium was reached. This effect was inhibited by anionic polypeptide fraction, which increased the amount of cholesterol within precipitable phospholipid vesicles, and decreased the rate of crystal formation. Fluorescence-labeled anionic polypeptide fraction revealed that anionic polypeptide fraction (with and without calcium) was primarily associated with vesicle aggregates.
Our data demonstrate that calcium and anionic polypeptide fraction have opposing effects on the process of cholesterol crystallization and the resultant crystal mass without influencing the crystal observation time of bile. These findings suggest that biliary proteins, in addition to being crystallization effectors by themselves, may further influence cholesterol crystallization and gallstone formation by interacting with calcium and possibly other elements that coexist in bile.
背景/目的：胆固醇结石含有钙和胆汁蛋白，但其在胆结石发病机制中的各自作用尚不清楚。我们研究了钙和一种主要的胆汁蛋白——阴离子多肽组分对胆汁中胆固醇结晶过程的影响。
从人胆汁中纯化阴离子多肽组分。制备由胆固醇、蛋黄卵磷脂和牛磺胆酸钠组成的模拟成石性人胆囊胆汁脂质浓度（分别为18 mM、37 mM和120 mM）的模型胆汁。通过相差显微镜观察结晶过程，并通过蔗糖密度梯度超速离心对可沉淀的胆固醇结构进行连续分离。
单独添加钙、阴离子多肽组分或两者一起添加均不影响胆汁的晶体观察时间（从过饱和开始到晶体首次出现所经过的时间）。然而，胆固醇沉淀和晶体形成的速率和数量均受到两者的影响。在达到明显平衡之前，钙以剂量依赖的方式增加了一水合胆固醇晶体的质量。这种作用被阴离子多肽组分抑制，阴离子多肽组分增加了可沉淀磷脂囊泡内的胆固醇量，并降低了晶体形成的速率。荧光标记的阴离子多肽组分显示，阴离子多肽组分（有钙和无钙）主要与囊泡聚集体相关。
我们的数据表明，钙和阴离子多肽组分对胆固醇结晶过程和最终的晶体质量具有相反的作用，而不影响胆汁的晶体观察时间。这些发现表明，胆汁蛋白除了自身作为结晶效应物外，还可能通过与钙以及胆汁中可能共存的其他元素相互作用，进一步影响胆固醇结晶和胆结石形成。
