Buscher H P, Gerok W, Köllinger M, Kurz G, Müller M, Nolte A, Schneider S
Institut für Organische Chemie und Biochemie, Universität Freiburg, Federal Republic of Germany.
Adv Enzyme Regul. 1988;27:173-92. doi: 10.1016/0065-2571(88)90016-7.
Photoaffinity labeling of plasma membrane subfractions from liver and of intact liver tissue with a photolabile bile salt derivative, the sodium salt of (7,7-azo-3 alpha,12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-aminoethanesulfonic acid, revealed that the hepatobiliary transport of bile salts is accomplished by transport systems different for sinusoidal uptake and canalicular secretion. Polypeptides with apparent Mr values 54,000 and 48,000 interact with bile salts at sinusoidal membrane, whereas a polypeptide with an apparent Mr of 100,000 is involved in bile salt secretion through the canalicular membrane. Photoaffinity labeling with photolabile derivatives of uncharged and cationic compounds provided evidence that the sinusoidal membrane polypeptides exhibit a broad binding specificity. Photoaffinity labeling studies and kinetic studies suggest that hepatic uptake of different amphipathic anions, uncharged compounds and even of cations is mediated by the sinusoidal transport systems which are involved in the uptake of bile salts. Relatively little is known about the specificity of the canalicular bile salt transport system. The fluorescent bile salt derivative, the sodium salt of (N-[7-(4-nitrobenzo-2-oxa-1,3-diazol)]-3 beta-amino-7 alpha, 12 alpha-dihydroxy-5 beta-cholan-24-oyl)-2-aminoethanesulfonic acid, is readily taken up into the hepatocytes of all acinar zones and may be used for the evaluation of the functional state of bile salt transport by fluorescence microscopy. Fluorescent microscopic studies with the fluorescent bile salt derivative showed that ascites hepatoma AS 30D cells do not have the ability to take up bile salts and demonstrated the absence of hepatobiliary bile salt transport in the solid Morris hepatoma 7777. Photoaffinity labeling studies revealed that in both tumor cell models, in hepatoma AS 30D and in Morris hepatoma 7777, the plasma membranes were devoid of the polypeptides having affinities to bile salts and amphipathic cations. A slight labeling of bile salt binding membrane polypeptides in plasma membranes from Morris hepatomas 9618A and TC 5123 opens the possibility to study transport in neoplastic hepatocytes.
用一种光不稳定的胆汁盐衍生物，即(7,7-偶氮-3α,12α-二羟基-5β-胆烷-24-酰基)-2-氨基乙烷磺酸钠，对肝脏质膜亚组分和完整肝脏组织进行光亲和标记，结果表明胆汁盐的肝胆转运是通过窦状隙摄取和胆小管分泌不同的转运系统来完成的。表观分子量为54,000和48,000的多肽在窦状隙膜处与胆汁盐相互作用，而表观分子量为100,000的多肽参与胆汁盐通过胆小管膜的分泌。用不带电荷和带阳离子的化合物的光不稳定衍生物进行光亲和标记，证明窦状隙膜多肽具有广泛的结合特异性。光亲和标记研究和动力学研究表明肝脏对不同的两亲性阴离子、不带电荷的化合物甚至阳离子的摄取是由参与胆汁盐摄取的窦状隙转运系统介导的。关于胆小管胆汁盐转运系统的特异性了解相对较少。荧光胆汁盐衍生物，即(N-[7-(4-硝基苯并-2-恶唑-1,3-二氮杂环戊二烯)]-3β-氨基-7α,12α-二羟基-5β-胆烷-24-酰基)-2-氨基乙烷磺酸钠，很容易被所有腺泡区的肝细胞摄取，并可用于通过荧光显微镜评估胆汁盐转运的功能状态。用荧光胆汁盐衍生物进行的荧光显微镜研究表明腹水肝癌AS 30D细胞没有摄取胆汁盐的能力，并证明实体型莫里斯肝癌7777中不存在肝胆胆汁盐转运。光亲和标记研究表明，在两种肿瘤细胞模型中，即肝癌AS 30D和莫里斯肝癌7777中，质膜都缺乏对胆汁盐和两亲性阳离子有亲和力的多肽。莫里斯肝癌9618A和TC 5123质膜中胆汁盐结合膜多肽的轻微标记为研究肿瘤肝细胞中的转运提供了可能性。
