Coupling of Na-H exchange and Na-K pump activity in cultured rat proximal tubule cells.
Coupling of Na-H exchange and Na-K pump activity in cultured rat proximal tubule cells.
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培养的大鼠近端小管细胞中 Na-H 交换和 Na-K 泵活性的耦合。
DOI：
10.1152/ajpcell.1986.251.5.c815
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Lechene,C
中科院分区：
文献类型：
--
作者：
Harris,RC;Seifter,JL;Lechene,C
采用电子探针分析和单个细胞微荧光pH分析，对40 ~ 50日龄的sd大鼠近端小管细胞（RPTC）进行3 d原代培养，研究Na-H交换。Na- k泵抑制后，1 mM阿米洛利可抑制初始净Na内流率87%。高钠细胞（0.114 mM K X mM P-1 X min-1）与低钠细胞（0.038 mM K X mM P-1 X min-1）相比，钾内流（Na-K泵活性的估估值）增加了约3倍。负载细胞质pH指示剂5-（和-6）羧基-4′，5′-二甲基荧光素的RPTC单细胞测量表明，在没有外部Na或存在酰胺的情况下，存在可逆的细胞内酸化。当通过添加和随后去除NH4Cl诱导细胞内酸化时，在没有外部Na或存在阿米洛利的情况下，细胞内pH的恢复受到抑制。使用类似的方案，发现细胞内酸化后，Na内流率增加了至少5.9倍，60 s时细胞内Na含量增加了3.15 +/- 0.64倍。与对照（未酸化）RPTC相比，在最初的60秒内，Na-K泵活性被抑制了50%，其次是Na-K泵活性的增加。阿米洛利（0.5 mM）抑制了酸化引起的Na内流增加，与对照组相比，持续酸化导致Na- k泵活性持续抑制。总之，这些结果表明，在我们的基础条件下，Na- h交换介导了大部分净Na流入RPTC，并且是维持细胞内pH稳态所必需的。在RPTC中，Na- h交换被细胞内酸化进一步激活，导致细胞内Na含量的净增加，进而刺激Na- k泵活性。Na-K泵活性的最初抑制可能是由于细胞内酸化的直接影响。
Na-H exchange was studied using electron probe analysis and microfluorescent pH analysis of individual cells, in 3-day primary cultures of rat proximal tubule cells (RPTC) obtained from 40- to 50-day-old Sprague-Dawley rats. After Na-K pump inhibition, the initial rate of net Na influx was inhibited 87% by 1 mM amiloride. K influx, an estimate of Na-K pump activity, was increased approximately three times in cells containing high Na (0.114 mM K X mM P-1 X min-1) compared with control cells containing low Na (0.038 mM K X mM P-1 X min-1). Single cell measurements of RPTC loaded with the cytoplasmic pH indicator 5- (and -6) carboxy-4',5'-dimethylfluorescein indicated that there was reversible intracellular acidification in the absence of external Na or in the presence of amiloride. When intracellular acidification was induced by the addition and subsequent removal of NH4Cl, recovery of intracellular pH was inhibited in the absence of external Na or in the presence of amiloride. Using a similar protocol, it was found that after intracellular acidification, the rate of Na influx increased at least 5.9 times, and intracellular Na content was increased 3.15 +/- 0.64 times at 60 s. There was an initial 50% inhibition of Na-K pump activity within the first 60 s compared with control (nonacidified) RPTC, secondarily followed by an increase in Na-K pump activity. Amiloride (0.5 mM) inhibited the acidification-induced increase in Na influx, and persistent acidification led to a persistent inhibition of Na-K pump activity compared with control. In summary, these results demonstrate that Na-H exchange mediates the majority of net Na influx into RPTC under our basal conditions and is necessary for maintenance of intracellular pH homeostasis. In RPTC, Na-H exchange is further activated by intracellular acidification, leading to a net increase in intracellular Na content, which secondarily stimulates Na-K pump activity. The initial inhibition of Na-K pump activity may be due to a direct effect of intracellular acidification.