Kino M, Nakamura A, Hopp L, Kuriyama S, Aviv A
J Cell Physiol. 1986 Oct;129(1):1-10. doi: 10.1002/jcp.1041290102.
The washout of Na+ isotopes from tissues and cells is quite complex and not well defined. To further gain insight into this process, we have studied 22Na+ washout from cultured Wistar rat skin fibroblasts and vascular smooth muscle cells (VSMCs). In these preparations, 22Na+ washout is described by a general three-exponential function. The exponential factor of the fastest component (k1) and the initial exchange rate constant (kie) of cultured fibroblasts decrease in magnitude in response to incubation in K+-deficient medium or in the presence of ouabain and increase in magnitude when the cells are incubated in a Ca++-deficient medium. As the magnitude of the kie declines (in the presence of ouabain) to the level of the exponential factor of the middle component (k2), 22Na+ washout is adequately described by a two-exponential function. When the kie is further diminished (in the presence of both ouabain and phloretin) to the range of the exponential factor of the slowest component (k3), the washout of 22Na+ is apparently monoexponential. Calculations of the cellular Na+ concentrations, based on the 22Na+ activity in the cells at the initiation of the washout experiments, and the medium specific activity agree with atomic absorption spectrometry measurements of the cellular concentration of this ion. Thus, all three components of 22Na+ washout from cultured rat cells are of cellular origin. Using the exponential parameters, compartmental analyses of two models (in parallel and in series) with three cellular Na+ pools were performed. The results indicate that, independent of the model chosen, the relative size of the largest Na+ pool is 92-93% in fibroblasts and approximately 96% in VSMCs. This pool is most likely to represent the cytosol.
组织和细胞中Na⁺同位素的洗脱过程相当复杂，目前尚未完全明确。为了更深入地了解这一过程，我们研究了培养的Wistar大鼠皮肤成纤维细胞和血管平滑肌细胞（VSMC）中²²Na⁺的洗脱情况。在这些样本中，²²Na⁺洗脱过程可用一个通用的三指数函数来描述。培养的成纤维细胞中，最快成分的指数因子（k1）和初始交换速率常数（kie）在低钾培养基中孵育或存在哇巴因时，其数值会降低；而当细胞在缺钙培养基中孵育时，其数值会升高。当kie的数值（在存在哇巴因的情况下）下降到中间成分的指数因子（k2）水平时，²²Na⁺洗脱过程可用一个双指数函数充分描述。当kie进一步降低（在同时存在哇巴因和根皮素的情况下）到最慢成分的指数因子（k3）范围内时，²²Na⁺的洗脱明显呈单指数形式。根据洗脱实验开始时细胞内²²Na⁺活性和培养基比活性计算得到的细胞内Na⁺浓度，与该离子细胞浓度的原子吸收光谱测量结果相符。因此，培养的大鼠细胞中²²Na⁺洗脱的所有三个成分均来源于细胞。利用指数参数，对具有三个细胞内Na⁺池的两个模型（并联和串联）进行了房室分析。结果表明，无论选择哪种模型，成纤维细胞中最大Na⁺池的相对大小为92 - 93%，VSMC中约为96%。这个池很可能代表细胞质溶胶。
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