Pritchard J B, Booz G W, Kleinzeller A
Am J Physiol. 1982 Apr;242(4):F415-22. doi: 10.1152/ajprenal.1982.242.4.F415.
The transport of D-mannose (Man) in flounder kidney was studied using renal clearance techniques in vivo and brush border membrane (BBM) vesicles in vitro. At plasma concentrations of 50-100 microM Man, the winter flounder (Pseudopleuronectes americanus) reabsorbed up to 70% of the filtered sugar. Man phosphates, but not free Man, accumulated in renal cells. Reabsorption of Man was reduced by phlorizin, D-glucose, methyl-alpha-D-glucoside, methyl-alpha-D-mannoside, and 2-deoxy-D-glucose. In BBM vesicles a Na+-dependent, phlorizin-sensitive overshoot in Man uptake (10 microM) was seen. Na+-dependent Man uptake was saturable, with an apparent Km of 127 microM. The transport properties for Man were identical in BBM vesicles from the winter flounder and southern flounder (Paralichthys lethostigma). The transport specificity was determined by cis-inhibition and trans-stimulation experiments with BBM. Glucose, galactose, 1,5-anhydro-D-mannitol (i.e., 1-deoxymannose), 2-deoxy-2-fluoro-D-glucose, and methyl-alpha-mannoside were shown to share the carrier-mediating mannose transport. 2-Deoxyglucose, methyl-alpha-2-deoxy-D-glucoside, and both the isomers (alpha and beta) of methyl-D-glucoside did not. In contrast, alpha-methyl-D-glucoside inhibited D-glucose transport both in vivo and in BBM vesicles. It is concluded that Man reabsorption in the flounder occurs via a Na+-cotransport system that also handles glucose but that differs from the glucose/methyl-alpha-D-glucoside reabsorptive pathway in that 1) an oxygen on C-1 is not required, and 2) an axial configuration for -OH on C-2 (C1 conformation) is readily accommodated.
利用体内肾清除技术和体外刷状缘膜（BBM）囊泡研究了比目鱼肾脏中D - 甘露糖（Man）的转运。在血浆中Man浓度为50 - 100微摩尔时，冬季比目鱼（美洲拟庸鲽）可重吸收高达70%的滤过糖。磷酸化的Man在肾细胞中积累，而游离Man则不会。根皮苷、D - 葡萄糖、甲基 - α - D - 葡萄糖苷、甲基 - α - D - 甘露糖苷和2 - 脱氧 - D - 葡萄糖可减少Man的重吸收。在BBM囊泡中观察到，在10微摩尔Man摄取时存在Na⁺依赖性、根皮苷敏感的摄取过冲现象。Na⁺依赖性Man摄取具有饱和性，表观Km为127微摩尔。冬季比目鱼和南方比目鱼（宽带副牙鲆）的BBM囊泡中Man的转运特性相同。通过BBM的顺式抑制和反式刺激实验确定了转运特异性。结果表明，葡萄糖、半乳糖、1,5 - 脱水 - D - 甘露糖醇（即1 - 脱氧甘露糖）、2 - 脱氧 - 2 - 氟 - D - 葡萄糖和甲基 - α - 甘露糖苷共享介导甘露糖转运的载体。2 - 脱氧葡萄糖、甲基 - α - 2 - 脱氧 - D - 葡萄糖苷以及甲基 - D - 葡萄糖苷的两种异构体（α和β）则不然。相比之下，α - 甲基 - D - 葡萄糖苷在体内和BBM囊泡中均抑制D - 葡萄糖转运。得出的结论是，比目鱼中Man的重吸收通过一种Na⁺共转运系统进行，该系统也处理葡萄糖，但与葡萄糖/甲基 - α - D - 葡萄糖苷重吸收途径不同，在于：1）C - 1位的氧不是必需的；2）C - 2位 - OH的轴向构型（C1构象）易于容纳。
