Ullrich K J, Capasso G, Rumrich G, Papavassiliou F, Klöss S
Pflugers Arch. 1977 Apr 25;368(3):245-52. doi: 10.1007/BF00585203.
The rate of active transport by the proximal renal tubule of amino acid (L-histidine), sugar (alpha-methyl-D-glycoside), H+ ions (glycodiazine), phosphate and para-aminohippurate was evaluated by measuring the zero net flux concentration difference (deltac) of these substances. In the case of calcium the electrochemical potential difference (delta + zF-CIdeltaphi/RT) was the criterion employed. The rate of isotonic Na+-absorption (JNa) was measured with the shrinking droplet method. The effect of ouabain on the transport of these substances was tested in the golden hamster and the effect of SITS (4-acetamido-4'isothiocyanatostilbene 2,2'-disulfonic acid) was observed in rats. Ouabain (1 mM) applied peritubularly incompletely inhibited JNa (80%), but in combination with acetazolamide (0.2 mM) the inhibition was almost complete (93%). In addition, ouabain inhibited the sodium coupled (secondary active) transport processes of L-histidine, alpha-methyl-D-glycoside, calcium and phosphate by more than 75%. It did not affect H+ (glycodiazine) transport and PAH transport was only slightly affected. When SITS (1 mM) was applied from both sides of the cell it inhibited H+ (glycodiazine) transport by 72% and reduced JNa by 38% when given from only the peritubular cell side. SITS (1 MM), however, had no significant affect on H+ secretion and sodium reabsorption if it was applied from only the luminal side. Furthermore it had no affect on the other transport processes tested, regardless of the cell side to which it was applied. When the HCO-3 buffer or physically related buffers were omitted from the perfusate the absorption of Na+ was reduced by 66%, phosphate by 44%, and L-histidine by 15%. All the other transport processes tested were not significantly affected. The data are consistent with the hypothesis that the active transport processes of histidine, alpha-methyl-D-glycoside and phosphate, which are located in the brush border, are driven by a sodium gradient which is abolished by ouabain. This may also apply to the Na+-Ca2+ countertransport located at the contraluminal cell side. The residual Na+ transport remaining in the presence of ouabain is likely to be passively driven by the continuing H+ transport which probably is driven directly by ATP. SITS seems to inhibit the exit step of HCO-3 from the cell and secondary to that, the luminal H+-Na+ exchange and consequently the Na+ reabsorption. In the absence of HCO-3 buffer in the perfusates the luminal H+-Na+ exchange seems to be affected and the pattern of inhibition of the other transport processes is almost the same as with SITS. The different effects on Pi reabsorption observed under these conditions might be explained by possible variations in intracellular pH.
通过测量氨基酸（L-组氨酸）、糖类（α-甲基-D-糖苷）、氢离子（甘氨双唑钠）、磷酸盐和对氨基马尿酸的零净通量浓度差（Δc），评估近端肾小管对这些物质的主动转运速率。对于钙，采用的标准是电化学势差（Δ + zF - CIdeltaphi/RT）。用收缩液滴法测量等渗Na⁺吸收速率（JNa）。在金黄仓鼠中测试了哇巴因对这些物质转运的影响，在大鼠中观察了SITS（4-乙酰氨基-4'-异硫氰基芪-2,2'-二磺酸）的作用。经肾小管周围施加1 mM哇巴因可不完全抑制JNa（80%），但与乙酰唑胺（0.2 mM）联合使用时，抑制作用几乎完全（93%）。此外，哇巴因抑制L-组氨酸、α-甲基-D-糖苷、钙和磷酸盐的钠偶联（继发性主动）转运过程超过75%。它不影响H⁺（甘氨双唑钠）转运，对PAH转运的影响也很小。当从细胞两侧施加1 mM SITS时，它抑制H⁺（甘氨双唑钠）转运72%，仅从肾小管周围细胞侧施加时，使JNa降低38%。然而，如果仅从管腔侧施加1 mM SITS，则对H⁺分泌和钠重吸收没有显著影响。此外，无论施加到哪一侧细胞，它对其他测试的转运过程均无影响。当灌注液中省略HCO₃缓冲液或物理相关缓冲液时，Na⁺吸收减少66%，磷酸盐减少44%，L-组氨酸减少15%。所有其他测试的转运过程均未受到显著影响。这些数据与以下假设一致，即位于刷状缘的组氨酸、α-甲基-D-糖苷和磷酸盐的主动转运过程由钠梯度驱动，而哇巴因可消除该梯度。这也可能适用于位于对腔细胞侧的Na⁺-Ca²⁺逆向转运。在哇巴因存在下剩余的Na⁺转运可能由持续的H⁺转运被动驱动，而H⁺转运可能直接由ATP驱动。SITS似乎抑制HCO₃从细胞的排出步骤，其次抑制管腔H⁺-Na⁺交换，从而抑制Na⁺重吸收。在灌注液中不存在HCO₃缓冲液时，管腔H⁺-Na⁺交换似乎受到影响，对其他转运过程的抑制模式与SITS几乎相同。在这些条件下观察到的对Pi重吸收的不同影响可能由细胞内pH的可能变化来解释。
