Schlattjan Jan Henrik, Fehsenfeld Heike, Greven Joachim
Department of Pharmacology and Toxicology, Aachen University, Aachen, Germany.
Arzneimittelforschung. 2003;53(12):837-43. doi: 10.1055/s-0031-1299838.
The effect of the dimeric bile acid analogue S 0960 (CAS 142974-51-4), a specific inhibitor of the apical sodium-dependent bile salt transporter (ASBT) in the ileum, on kidney function was studied by clearance experiments in anesthetized rats. Additional experiments were performed on proximal tubular cells freshly isolated from rat kidney cortex and enriched by nycodenz density gradient centrifugation. The clearance studies, which were performed after a 5 h bile duct ligation, revealed a marked rise of the 3H-taurocholate clearance (from 85.4 +/- 15.7 to 371.1 +/- 86.0 microliters/min 100 g b.w., p < 0.05) and a considerable fall of the fractional tubular 3H-taurocholate reabsorption (from 90.2 +/- 1.72 to 68.2 +/- 7.50%, p < 0.05) after S 0960 at a dose of 10 mg/kg i.v. whereas the glomerular filtration rate did not significantly change (from 919 +/- 165 to 1055 +/- 162 microliters/min/100 g b.w.). Isolated proximal tubular cells showed a significant accumulation of 3H-taurocholate. The 3H-taurocholate cell/bath concentration ratio amounted to 3.34 +/- 0.17 at a 3H-taurocholate bath concentration of 3 x 10(-7) mol/l. LiCl (10(-3) mol/l), which is known to inhibit sodium-dependent transport processes in the kidney, markedly diminished cellular 3H-taurocholate uptake (by 65.8%) whereas probenecid (CAS 57-66-9, 10(-4) mol/l), the classical inhibitor of the basolateral organic acid transporter in the kidney, did not significantly affect 3H-taurocholate uptake. This finding indicates that transport of taurocholate by the basolaterally located organic acid transporter is not involved in the uptake process. The kinetic studies revealed an apparent K(m) value of 31 mumol/l and a Vmax value of 6.7 mumol/l cell water/min for tubular 3H-taurocholate uptake. At concentrations > 30 mumol/l S 0960 virtually completely inhibited cellular 3H-taurocholate uptake. 3H-taurocholate uptake was half-maximally inhibited at a S 0960 concentration of 5.8 mumol/l. The results of this functional study are in line with recent molecular evidence that the apical sodium-dependent bile salt transporters in kidney and ileum are identical and demonstrate that S 0960 is a potent inhibitor of the apical sodium-dependent taurocholate transporter in the kidney which augments the renal clearance of 3H-taurocholate. Compounds such as S 0960 may be of special therapeutical value in patients with extrahepatic cholestasis and elevated levels of plasma bile acids.
通过对麻醉大鼠进行清除实验，研究了二聚体胆汁酸类似物S 0960（化学物质登记号142974 - 51 - 4）对肾功能的影响。S 0960是回肠顶端钠依赖性胆盐转运体（ASBT）的特异性抑制剂。另外，对从大鼠肾皮质新鲜分离并用尼可地密度梯度离心法富集的近端肾小管细胞进行了实验。在胆管结扎5小时后进行的清除研究显示，静脉注射剂量为10mg/kg的S 0960后，3H - 牛磺胆酸盐清除率显著升高（从85.4±15.7微升/分钟·100克体重升至371.1±86.0微升/分钟·100克体重，p < 0.05），肾小管对3H - 牛磺胆酸盐的重吸收分数显著下降（从90.2±1.72%降至68.2±7.50%，p < 0.05），而肾小球滤过率无显著变化（从919±165微升/分钟/100克体重升至1055±162微升/分钟/100克体重）。分离的近端肾小管细胞显示出3H - 牛磺胆酸盐的显著蓄积。在3H - 牛磺胆酸盐浴液浓度为3×10⁻⁷mol/L时，3H - 牛磺胆酸盐细胞/浴液浓度比为3.34±0.17。已知抑制肾脏中钠依赖性转运过程的LiCl（10⁻³mol/L）显著降低细胞对3H - 牛磺胆酸盐的摄取（降低65.8%），而肾脏基底外侧有机酸转运体的经典抑制剂丙磺舒（化学物质登记号57 - 66 - 9，10⁻⁴mol/L）对3H - 牛磺胆酸盐摄取无显著影响。这一发现表明，基底外侧有机酸转运体介导的牛磺胆酸盐转运不参与摄取过程。动力学研究显示，肾小管对3H - 牛磺胆酸盐摄取的表观K(m)值为31μmol/L，Vmax值为6.7μmol/L细胞水/分钟。当浓度>30μmol/L时，S 0960几乎完全抑制细胞对3H - 牛磺胆酸盐的摄取。在S 0960浓度为5.8μmol/L时，3H - 牛磺胆酸盐摄取被抑制一半。这项功能研究的结果与最近的分子证据一致，即肾脏和回肠中的顶端钠依赖性胆盐转运体相同，并表明S 0960是肾脏中顶端钠依赖性牛磺胆酸盐转运体的有效抑制剂，可增加3H - 牛磺胆酸盐的肾脏清除率。像S 0960这样的化合物可能对肝外胆汁淤积和血浆胆汁酸水平升高的患者具有特殊的治疗价值。
