Rick R
Department of Physiology and Biophysics, University of Alabama, Birmingham.
J Membr Biol. 1992 May;127(3):227-36. doi: 10.1007/BF00231510.
Intracellular ion concentrations were determined in split skins of Rana pipiens using the technique of electron microprobe analysis. Under control conditions, principal cells and mitochondria-rich cells (MR cells) had a similar intracellular ion composition, only the Cl concentration in MR cells was significantly lower. Inhibition of transepithelial Na transport by low concentrations of ouabain (2 x 10(-6) M, inner bath) resulted in a Na concentration increase of principal cells from 10.9 to 54.3 mmol/kg wet wt. The increase was completely abolished by simultaneous application of amiloride (10(-4) M, outer bath). Amiloride alone resulted in a significant decrease of the Na concentration to 6.1 mmol/kg. w.w. Among MR cells, two different groups of cells could be distinguished; cells that showed a Na increase after ouabain which was even larger than that in principal cells and cells that did not respond to ouabain. In about half of all ouabain-sensitive MR cells the Na increase could be prevented by amiloride. According to these results, a subpopulation of MR cells displays the transport characteristics expected for a transepithelial Na transport compartment, an apical amiloride-sensitive Na influx and a basal ouabain-inhibitable Na efflux. Given the small number of cells, however, it is unlikely that this subtype of MR cells contributes significantly to the overall rate of transepithelial Na transport.
利用电子微探针分析技术测定了牛蛙离体皮肤中的细胞内离子浓度。在对照条件下，主细胞和富含线粒体的细胞（MR细胞）具有相似的细胞内离子组成，只是MR细胞中的Cl浓度显著较低。低浓度哇巴因（2×10⁻⁶ M，内浴）抑制跨上皮Na转运导致主细胞的Na浓度从10.9 mmol/kg湿重增加到54.3 mmol/kg。同时应用氨氯吡咪（10⁻⁴ M，外浴）可完全消除这种增加。单独使用氨氯吡咪会导致Na浓度显著降低至6.1 mmol/kg湿重。在MR细胞中，可以区分出两组不同的细胞；一组细胞在哇巴因作用后Na增加，甚至比主细胞中的增加幅度还大，另一组细胞对哇巴因无反应。在所有对哇巴因敏感的MR细胞中，约一半细胞的Na增加可被氨氯吡咪阻止。根据这些结果，MR细胞的一个亚群表现出跨上皮Na转运区室预期的转运特征，即顶端氨氯吡咪敏感的Na内流和基底哇巴因抑制的Na外流。然而，鉴于细胞数量较少，这种MR细胞亚型不太可能对跨上皮Na转运的总体速率有显著贡献。
