Adachi Y, Roy-Chowdhury J, Roy-Chowdhury N, Kinne R, Tran T, Kobayashi H, Arias I M
Second Department of Internal Medicine, Kinki University School of Medicine, Osaka.
J Biochem. 1990 May;107(5):749-54. doi: 10.1093/oxfordjournals.jbchem.a123120.
In order to characterize the mechanism for bilirubin transport in the liver, the uptake of bilirubin diglucuronide (BDG) into purified sinusoidal plasma membrane vesicles was investigated. BDG uptake was saturable, and was inhibited by sulfobromophthalein and unconjugated bilirubin, but was not affected by sodium taurocholate. BDG uptake was sodium-independent and was stimulated by intravesicular bilirubin or BDG (trans-stimulation). BDG transport showed strong potential sensitivity; vesicle inside-negative membrane potential created by different anion gradients inhibited BDG uptake whereas vesicle inside-positive membrane potential generated by potassium gradients and valinomycin markedly stimulated BDG transport. These data suggest that BDG, sulfobromophthalein, and probably unconjugated bilirubin share a common transporter in liver cells which is sodium independent, membrane-potential-dependent and capable of exchange. The direction of transport in vivo may be governed by the intracellular concentration of BDG and of other yet unidentified organic anions sharing this transporter.
为了阐明肝脏中胆红素转运的机制，研究了胆红素二葡萄糖醛酸酯（BDG）在纯化的肝血窦质膜囊泡中的摄取情况。BDG的摄取是可饱和的，并且受到磺溴酞钠和未结合胆红素的抑制，但不受牛磺胆酸钠的影响。BDG的摄取不依赖于钠，并且受到囊泡内胆红素或BDG的刺激（反式刺激）。BDG转运表现出很强的电位敏感性；由不同阴离子梯度产生的囊泡内负膜电位抑制BDG摄取，而由钾梯度和缬氨霉素产生的囊泡内正膜电位则显著刺激BDG转运。这些数据表明，BDG、磺溴酞钠以及可能的未结合胆红素在肝细胞中共享一种共同的转运体，该转运体不依赖于钠，依赖于膜电位，并且能够进行交换。体内转运的方向可能由BDG以及其他尚未确定的共享该转运体的有机阴离子的细胞内浓度所决定。
