胆盐与磷酸钙的相互作用

胆汁的pH条件下(pH=6～8)，应该生成无定形磷酸钙(ACP)，而在胆结石中磷酸钙通常以羟基磷灰石的形式出现.利用谱学方法研究了ACP与胆盐的作用.结果表明，胆盐以胶团的形式与ACP作用，在溶液中形成复合胶团，使其溶解度增加.不同类型胆盐与ACP的作用能力不同：脱氧胆酸钠(NaDC) > 牛磺胆酸钠(NaTC) > 胆酸钠(NaC).胆盐与ACP中结合钙的亲和能力大于结合钙的亲和能力，使ACP在胆汁的环境下容易转化为羟基磷灰石.

Interaction of Bile Salts with Calcium Phosphate

Insoluble calcium salts are always observed in different types of gallstones, such as calcium phosphate, calcium carbonate and calcium bilirubinate. The major form of calcium phosphate in gallstone is calcium hydroxyapatite (HAP). Understanding of the transformation of amorphous calcium phosphate (ACP) into HAP in bile is necessary to prevent gallstones formation. The aim of this paper was to examine the interaction of bile salts, an important bio-surfactant, with ACP using vibrational spectroscopy. ACP [(Ca9－x(HPO4)2x(PO4)6－2x)],calcium hydrogen phosphate(CaHPO4•2H2O) and calcium phosphate(Ca3(PO4)2) precipitations were synthesized. CaHPO4 reacted with NaDC (0.1 mol•L－1) completely in solution, and mixed complex(NamCan(DC)2n＋m) precipitate formed. In contrast, only part of Ca3(PO4)2 reacted with NaDC, and the aggregate of NaDC in solution increased by Ca2＋bridge. It indicated that the micelle of NaDC bound to Ca2＋ on the solid surface of both CaHPO4 and Ca3(PO4)2, and the reactivity of CaHPO4 was more stronger than that of Ca3(PO4)2. ACP reacted with NaDC, NaTC and NaC respectively. The results demonstrated that the solubility of ACP increased with increase of bile salts content in solution. The reacting capacity of bile salts for ACP has the following order: NaDC >NaTC >NaC. The affinity of bile salts micelle to calcium binding to in ACP is stronger than binding to PO43－. Therefore, ACP transfers easily into HAP under bile condition.