Smith D J, Grossbard M, Gordon E R, Boyer J L
Am J Physiol. 1987 Apr;252(4 Pt 1):G479-84. doi: 10.1152/ajpgi.1987.252.4.G479.
Taurocholate transport was analyzed in a well characterized, polarized hepatocyte preparation from the small skate (Raja erinacea), an analbuminemic species that does not synthesize bile acids. In addition, the effect of sodium omission, bovine albumin, ovalbumin, and bovine gamma-globulin on the uptake of taurocholate was studied. Uptake could be divided into nonsaturable (0.48 pmol X min-1 X mg protein-1. microM-1) and saturable components (Km, 32.5 microM and Vmax 110 pmol X min-1 X mg protein-1). No evidence for sodium dependence could be obtained. Glycocholate competitively inhibited taurocholate uptake. The initial rate of taurocholate uptake was also inhibited by sulfobromophthalein, N-(4-azido-2-nitrophenyl)-2-aminoethyl sulfonate, and 4,4'-diisothiocyanostylbene-2,2'-disulfonic acid but not lactate or alanine. Hepatic uptake of taurocholate in albumin solutions (2.5%) was twice as great as expected from estimates of the free taurocholate concentration. In contrast, equimolar concentrations of ovalbumin or bovine gamma-globulin had no effect on measured rates of taurocholate uptake and no evidence for a specific albumin receptor could be found on these hepatocytes by 125I-albumin binding. These studies indicate that a carrier-mediated, sodium-independent transport system for taurocholate uptake is present in skate hepatocytes that is not driven solely by the free concentration of taurocholate.
在一种特征明确的、来自小鳐（Raja erinacea）的极化肝细胞制剂中分析了牛磺胆酸盐转运情况，小鳐是一种不合成胆汁酸的无白蛋白血症物种。此外，研究了钠缺失、牛血清白蛋白、卵清蛋白和牛γ球蛋白对牛磺胆酸盐摄取的影响。摄取可分为非饱和成分（0.48 pmol·min⁻¹·mg蛋白⁻¹·μM⁻¹）和饱和成分（Km为32.5 μM，Vmax为110 pmol·min⁻¹·mg蛋白⁻¹）。未获得钠依赖性的证据。甘氨胆酸盐竞争性抑制牛磺胆酸盐摄取。牛磺胆酸盐摄取的初始速率也受到磺溴酞、N-(4-叠氮-2-硝基苯基)-2-氨基乙基磺酸盐和4,4'-二异硫氰酸芪-2,2'-二磺酸的抑制，但不受乳酸或丙氨酸的抑制。在白蛋白溶液（2.5%）中肝脏对牛磺胆酸盐的摄取量是根据游离牛磺胆酸盐浓度估计值的两倍。相比之下，等摩尔浓度的卵清蛋白或牛γ球蛋白对测量的牛磺胆酸盐摄取速率没有影响，并且通过¹²⁵I-白蛋白结合在这些肝细胞上未发现特异性白蛋白受体的证据。这些研究表明，在鳐肝细胞中存在一种载体介导的、不依赖钠的牛磺胆酸盐摄取转运系统，该系统并非仅由牛磺胆酸盐的游离浓度驱动。
