Intracellular-free magnesium in the smooth muscle of guinea pig taenia caeci: a concomitant analysis for magnesium and pH upon sodium removal
Intracellular-free magnesium in the smooth muscle of guinea pig taenia caeci: a concomitant analysis for magnesium and pH upon sodium removal
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豚鼠盲肠绦虫平滑肌中的细胞内游离镁：脱钠后镁和 pH 值的伴随分析
DOI：
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
T. Tomita
中科院分区：
文献类型：
--
作者：
S. Nakayama;H. Nomura;T. Tomita
本研究旨在研究豚鼠盲肠带绦虫细胞内游离镁离子浓度([镁]i)的调节。为了评价钙离子对Na(+)依赖的镁离子排出机制(Na(+)-镁离子交换)的相互作用，在含钙溶液中考察了Na+的去除(N-甲基-D-氨基葡萄糖胺取代)的影响。由于无Na(+)溶液中Phi的变化干扰了仅用~(31)P核磁共振谱中的β-ATP峰的单一化学位移来估算[Mg~(2+)]_i，因此根据伽马峰和β峰的化学位移同时估算了[Mg~(2+)]_i和Phi。当胞外Na+被N-甲基-D-氨基葡萄糖胺取代时，[Mg~(2+)]i可逆地升高。在无镁溶液中，[Mg2+]i的这种增加被消除，而在过量的Mg2+溶液中，这种增加被增强。在Na+的去除和再吸收过程中，ATP含量变化不大，说明[Mg~(2+)]i的变化不是由ATP释放的Mg~(2+)引起的，燃料限制也不会抑制Mg~(2+)挤压系统。无论细胞外的镁离子浓度如何，在无Na(+)的溶液中观察到缓慢的酸化和通过重新接纳Na+引起的一过性碱中毒。当细胞外Ca~(2+)浓度从正常(2.4 mM)增加到12 mM时，Na+的清除仅引起[Mg~(2+)]i的轻微升高，而同样的缓慢酸中毒也可观察到，表明细胞外Ca~(2+)抑制了Mg~(2+)内流，细胞内Ca~(2+)与[Mg~(2+)]~(2+)的竞争使[Mg~(2+)]~(2+)的升高可以忽略不计。这些结果表明，即使在生理条件下，Na(+)-Mg~(2+)交换也是维持低[Mg~(2+)]i的主要机制。
This study is concerned with the regulation of intracellular-free Mg2+ concentration ([Mg2+]i) in the smooth muscle of guinea pig taenia caeci. To assess an interaction of Ca2+ on the Na(+)-dependent Mg(2+)- extrusion mechanism (Na(+)-Mg2+ exchange), effects of Na+ removal (N- methyl-D-glucamine substitution) were examined in Ca(2+)-containing solutions. As changes in pHi in Na(+)-free solutions perturb estimation of [Mg2+]i using the single chemical shift only of the beta-ATP peak in 31P NMR (nuclear magnetic resonance) spectra, [Mg2+]i and pHi were concomitantly estimated from the chemical shifts of the gamma- and beta- peaks. When extracellular Na+ was substituted with N-methyl-D- glucamine, [Mg2+]i was reversibly increased. This increase in [Mg2+]i was eliminated in Mg(2+)-free solutions and enhanced in excess Mg2+ solutions. ATP content fluctuated little during removal and readmission of Na+, indicating that [Mg2+]i changes were not induced by Mg2+ release from ATP, and that Mg(2+)-extruding system would not be inhibited by fuel restriction. A slow acidification in Na(+)-free solutions and transient alkalosis by a readmission of Na+ were observed regardless of the extracellular Mg2+ concentration. When the extracellular Ca2+ concentration was increased from normal (2.4 mM) to 12 mM, only a marginal increase in [Mg2+]i was caused by Na+ removal, whereas a similar slow acidosis was observed, indicating that extracellular Ca2+ inhibits Mg2+ entry, and that the increase in [Mg2+]i is negligible through competition between Mg2+ and Ca2+ in intracellular sites. These results imply that Na(+)-Mg2+ exchange is the main mechanism to maintain low [Mg2+]i even under physiological conditions.
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DOI：
10.1016/s0021-9258(18)66886-3
发表时间：
1986-11
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
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DOI：
10.1152/ajpcell.1986.250.3.c442
发表时间：
1986
期刊：
The American journal of physiology
影响因子：
--
作者：
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DOI：
10.1152/ajpcell.1986.251.5.c687
发表时间：
1986
期刊：
The American journal of physiology
影响因子：
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作者：
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影响因子：
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DOI：
10.1073/pnas.86.8.2981
发表时间：
1989
影响因子：
11.1
作者：
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通讯作者：
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