Stevens R D, Lack L, Killenberg P G
Department of Medicine, Duke University Medical Center, Durham, NC 27710.
J Lipid Res. 1991 Apr;32(4):621-7.
The effect of sulfate esterification of the 3 alpha- or 7 alpha-hydroxyl groups of taurochenodeoxycholate on calcium binding was studied at 0.154 M NaCl in the presence and absence of phosphatidylcholine using a calcium electrode. For comparison, similar studies were made with taurochenodeoxycholate, taurodeoxycholate, and taurocholate. No high affinity calcium binding was demonstrable for any of these bile salts in pre-micellar solutions. Taurine-conjugated bile salts have greater affinity for calcium when in a micellar form. At elevated bile salt concentrations, the calcium binding of unsulfated dihydroxy taurine conjugates was similar to that of the monosulfate esters of taurochenodeoxycholate. The presence of phosphatidylcholine decreased calcium binding of the unsulfated dihydroxy bile salts and slightly increased calcium binding by taurocholate. However, the addition of phosphatidylcholine to monosulfate esters of taurochenodeoxycholate results in large increments in calcium binding. The results indicate that increased calcium binding due to the presence of phosphatidylcholine in bile salt solutions depends, in part, on the hydrophilicity of the bile salt and that the interaction of monosulfate esters of taurochenodeoxycholate with phosphatidylcholine leads to the formation of a high affinity calcium binding site.
在0.154M氯化钠溶液中，使用钙电极，研究了牛磺鹅去氧胆酸3α-或7α-羟基硫酸酯化对钙结合的影响，实验中存在和不存在磷脂酰胆碱。作为对照，对牛磺鹅去氧胆酸、牛磺脱氧胆酸和牛磺胆酸进行了类似研究。在胶束前溶液中，这些胆汁盐均未表现出高亲和力的钙结合。牛磺酸结合型胆汁盐在胶束形式下对钙具有更高的亲和力。在胆汁盐浓度升高时，未硫酸化的二羟基牛磺酸共轭物的钙结合与牛磺鹅去氧胆酸单硫酸酯相似。磷脂酰胆碱的存在降低了未硫酸化二羟基胆汁盐的钙结合，并略微增加了牛磺胆酸的钙结合。然而，向牛磺鹅去氧胆酸单硫酸酯中添加磷脂酰胆碱会导致钙结合大幅增加。结果表明，胆汁盐溶液中磷脂酰胆碱的存在导致钙结合增加，部分取决于胆汁盐的亲水性，并且牛磺鹅去氧胆酸单硫酸酯与磷脂酰胆碱的相互作用导致形成高亲和力的钙结合位点。
