Holzinger F, Schteingart C D, Ton-Nu H T, Eming S A, Monte M J, Hagey L R, Hofmann A F
Department of Medicine, University of California, San Diego 92093-0813, La Jolla 92093-0813, USA.
Hepatology. 1997 Nov;26(5):1263-71. doi: 10.1002/hep.510260526.
Studies were performed to characterize hepatic and intestinal transport, as well as biotransformation during transport, of a spectrum of fluorescent bile acids containing a fluorophore attached to the side chain. The following two classes of compounds were studied: 1) aminofluorescein (amF) coupled directly to the carboxylic group of a bile acid which was cholic, ursodeoxycholic, or cholylglycine; and 2) nitrobenzoxadiazolyl (NBD) coupled to the epsilon-amino group of a lysine conjugated bile acid, which was cholic or ursodeoxycholic. Fluorescein, a cholephilic organic anion, was studied as a control. Fluorescent bile acids were synthesized and their structures confirmed by nuclear magnetic resonance and mass spectrometry. Using the biliary fistula rat, hepatic transport, biotransformation, and choleretic activity were defined; intestinal absorption was assessed by jejunal or ileal perfusion studies. All fluorescent bile acids had hepatic transport maxima about one-sixth that reported for cholyltaurine, but derivatives of cholylglycine were transported best. Bile acids underwent little (<5%) biotransformation during hepatocyte transport. Only the amF conjugate of cholylglycine had normal choleretic activity; other compounds were hypocholeretic or cholestatic. In contrast, fluorescein was well transported, was partly glucuronidated, and had normal choleretic activity. NBD-tagged, but not amF-tagged, bile acids were actively transported by the intestine (ileum > jejunum), and no fluorescent bile acid had passive intestinal permeability; NBD-tagged bile acids were biotransformed during intestinal transport (jejunum > ileum). We conclude that the structure of the fluorophore as well as that of the bile acid influences transport by the hepatocyte and enterocyte. These fluorescent bile acids differ from fluorescein in being impermeable to cell membranes and undergoing little biotransformation during hepatocyte transport. Of these fluorescent bile acids, cholylglycylamF has hepatocyte transport and choleretic properties most closely resembling those of a natural bile acid.
开展了多项研究，以表征一系列在侧链连接有荧光团的荧光胆汁酸的肝脏和肠道转运，以及转运过程中的生物转化。研究了以下两类化合物：1）直接与胆酸、熊去氧胆酸或甘氨胆酸的羧基偶联的氨基荧光素（amF）；2）与胆酸或熊去氧胆酸的赖氨酸共轭物的ε-氨基偶联的硝基苯并恶二唑基（NBD）。作为对照，研究了亲胆有机阴离子荧光素。合成了荧光胆汁酸，并通过核磁共振和质谱确认了其结构。使用胆管瘘大鼠，确定了肝脏转运、生物转化和利胆活性；通过空肠或回肠灌注研究评估肠道吸收。所有荧光胆汁酸的肝脏转运最大值约为牛磺胆酸报道值的六分之一，但甘氨胆酸衍生物的转运效果最佳。胆汁酸在肝细胞转运过程中发生的生物转化很少（<5%）。只有甘氨胆酸的amF共轭物具有正常的利胆活性；其他化合物为利胆作用减弱或胆汁淤积。相比之下，荧光素转运良好，部分发生葡萄糖醛酸化，且具有正常的利胆活性。NBD标记而非amF标记的胆汁酸可被肠道（回肠>空肠）主动转运，且没有荧光胆汁酸具有被动肠道通透性；NBD标记的胆汁酸在肠道转运过程中发生生物转化（空肠>回肠）。我们得出结论，荧光团的结构以及胆汁酸的结构会影响肝细胞和肠细胞的转运。这些荧光胆汁酸与荧光素的不同之处在于它们不能透过细胞膜，且在肝细胞转运过程中发生的生物转化很少。在这些荧光胆汁酸中，甘氨胆酰amF的肝细胞转运和利胆特性与天然胆汁酸最为相似。
