Deppe C E, Heering P J, Tinel H, Kinne-Saffran E, Grabensee B, Kinne R K
Max-Planck-Institut für molekulare Physiologie, Abteilung Epithelphysiologie, Dortmund.
Exp Nephrol. 1997 Nov-Dec;5(6):471-80.
We investigated the influence of cyclosporine A (CsA) on key plasma membrane ion transport systems Na+/K(+)-ATPase, Na+/K+/2Cl- cotransporter, and H+/K(+)-ATPase in MDCK cells and two subtypes, C7 and C11, serving as a model system to study principal (C7) and intercalated (C11) cell properties of the distal nephron. The transport activity of Na+/K(+)-ATPase was significantly decreased in all cell types on CsA administration (8 x 10(-6) M) for 2 days, whereas the protein levels of Na+/K(+)-ATPase alpha-subunit in plasma membranes isolated from MDCK, C7, and C11 cells remained unchanged. The transport activity of Na+/K+/2Cl- cotransporter was significantly inhibited by CsA only in MDCK and C11 cells, but again plasma membrane protein levels were not altered. In contrast, C7 cell plasma membranes showed an increase of transport protein content, although the Na+/K+/2Cl- cotransporter activity was not affected by CsA. The H+/K(+)-ATPase transport activity remained unchanged in all three cell types. These data indicate that in C7 cells CsA might induce insertion of transporters into the plasma membrane, thus compensating the decrease of transport activity observed in MDCK and C11 cells. Furthermore, CsA significantly inhibited cell proliferation at 4 x 10(-6) M for C7 and C11 cells and at 8 x 10(-6) M for MDCK cells. Proliferation was completely abolished at 1.6 x 10(-5) M CsA. After 48 h of CsA incubation, the intracellular sodium concentration increased in all three different cell types; however, it stayed within the physiological range of mammalian cells. We, therefore, suggest that CsA is capable of reducing Na+/K(+)-ATPase and Na+/K+/2Cl- cotransporter activities in cells of the distal nephron, thereby contributing to the hyperkalemia observed in patients treated with CsA.
我们研究了环孢素A（CsA）对MDCK细胞以及作为研究远端肾单位主细胞（C7）和闰细胞（C11）特性模型系统的两个亚型C7和C11中关键质膜离子转运系统钠钾ATP酶、钠钾氯协同转运蛋白和氢钾ATP酶的影响。给予CsA（8×10⁻⁶ M）2天后，所有细胞类型中钠钾ATP酶的转运活性均显著降低，而从MDCK、C7和C11细胞分离的质膜中钠钾ATP酶α亚基的蛋白质水平保持不变。钠钾氯协同转运蛋白的转运活性仅在MDCK和C11细胞中被CsA显著抑制，但质膜蛋白水平再次未改变。相比之下，C7细胞质膜显示转运蛋白含量增加，尽管钠钾氯协同转运蛋白活性不受CsA影响。在所有三种细胞类型中，氢钾ATP酶的转运活性保持不变。这些数据表明，在C7细胞中，CsA可能诱导转运蛋白插入质膜，从而补偿在MDCK和C11细胞中观察到的转运活性降低。此外，CsA在4×10⁻⁶ M时显著抑制C7和C11细胞的增殖，在8×10⁻⁶ M时抑制MDCK细胞的增殖。在1.6×10⁻⁵ M CsA时增殖完全被抑制。CsA孵育48小时后，所有三种不同细胞类型中的细胞内钠浓度均升高；然而，它仍保持在哺乳动物细胞的生理范围内。因此，我们认为CsA能够降低远端肾单位细胞中钠钾ATP酶和钠钾氯协同转运蛋白的活性，从而导致接受CsA治疗的患者出现高钾血症。
