Inhibition of the serum‐dependent, amiloride‐sensitive sodium transport pathway in human fibroblasts by extracellular divalent cations
Inhibition of the serum‐dependent, amiloride‐sensitive sodium transport pathway in human fibroblasts by extracellular divalent cations
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细胞外二价阳离子抑制人成纤维细胞中血清依赖性、阿米洛利敏感的钠转运途径
DOI：
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发表时间：
1982
影响因子：
5.6
通讯作者：
M. Villereal
中科院分区：
文献类型：
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作者：
M. Villereal
在名义上无钙、无镁的培养基中，去血清人成纤维细胞中的钠内流显著更高（17.8 ± 1.9 μmole/g prot/min），高于在含1.8 mM Ca和1 mM Mg的培养基中测得的值（10.9 ± 0.7 μmole/g prot/min），并显著刺激（44.1 ± 6.1 μmole/g prot/min），表明钙离子内流增加不是血清激活阿米洛利敏感性Na内流途径的必要条件。向低Ca、低Mg培养基中的血清剥夺细胞中添加2 mM乙二胺四乙酸（EDTA）也导致Na内流的显著刺激（40.4 ± 3.7 μmole/g prot/min），而向存在FBS的低Ca、低Mg培养基中测定的细胞中添加EDTA对Na内流无显著影响（45.3 ± 4.1 μmole/g prot/min）。因此，FBS和EDTA的刺激作用不是相加的。在不同浓度阿米洛利存在下的动力学分析表明，EDTA刺激的Na内流通过阿米洛利敏感的Na途径发生。在不含Ca和Mg的细胞中，Na内流的激活可通过向测定培养基中加入Ca或Mg而容易地逆转。对于在无血清培养基中测定的细胞，产生50% Na内流抑制所需的Ca浓度为52 ± 7.6 μM（n = 3），对于在存在10% FBS的情况下测定的细胞，为272 ± 29 μM（n = 3）。在生理Ca浓度（1.8 mM）的Na流入最大限度地抑制钙在存在和不存在的血清。由于1.8 mM Ca培养基中的Na内流在存在血清的情况下比在不存在血清的情况下高2.5倍，因此这些数据表明血清诱导的阿米洛利敏感性Na转运途径的K，for Ca调节的变化不足以解释人成纤维细胞中Na内流的血清刺激。
Sodium influx in serum‐deprived human fibroblasts in a nominally Ca‐free, Mg‐free medium is significantly higher (17.8 ± 1.9 μmole/g prot/min) than that measured in a medium containing 1.8 mM Ca and 1 mM Mg (10.9 ± 0.7 μmole/g prot/min), and is stimulated dramatically (44.1 ± 6.1 μmole/g prot/min) by the addition of 10% fetal bovine serum (FBS), suggesting that an enhanced influx of Ca ions is not a necessary condition for serum activation of the amiloride‐sensitive Na influx pathway. The addition of 2 mM ethylenediaminetetraacetic acid (EDTA) to serum‐deprived cells in a low Ca, low Mg medium also results in a dramatic stimulation of Na influx (40.4 ± 3.7 μmole/g prot/min), while the addition of EDTA to cells assayed in a low Ca, low Mg medium in the presence of FBS has no significant effect on Na influx (45.3 ± 4.1 μmole/g prot/min). Thus, the stimulatory effects of FBS and EDTA are not additive. Kinetic analysis in the presence of varying amiloride concentrations indicate that the EDTA‐stimulated Na influx occurs via the amiloride‐sensitive Na pathway. The activation of Na influx in cells rinsed free of Ca and Mg Can be readily reversed by the addition of Ca or Mg to the assay medium. The Ca concentration required to give 50% inhibition of Na influx is 52 ± 7.6 μM (n = 3) for cells assayed in serum‐free medium and 272 ± 29 μM (n = 3) for cells assayed in the presence of 10% FBS. At physiological Ca concentrations (1.8 mM) the Na influx is maximally inhibited by Ca both in the presence and absence of serum. Since Na influx in 1.8 mM Ca medium is 2.5‐fold higher in the presence of serum than in its absence, these data suggest that the serum‐induced change in the K, for Ca modulation of the amiloride‐sensitive Na transport pathway is not sufficient to explain the serum stimulation of Na influx in human fibroblats.