Mechanisms for monovalent cation-dependent depletion of intracellular Mg2+:Na(+)-independent Mg2+ pathways in guinea-pig smooth muscle.
Mechanisms for monovalent cation-dependent depletion of intracellular Mg2+:Na(+)-independent Mg2+ pathways in guinea-pig smooth muscle.
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豚鼠平滑肌细胞内 Mg2 :Na( ) 独立 Mg2 通路单价阳离子依赖性消耗的机制。
DOI：
10.1113/jphysiol.2003.047795
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
Matsubara,Tatsuaki
中科院分区：
文献类型：
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作者：
Nakayama,Shinsuke;Nomura,Hideki;Smith,LorraineM;Clark,JosephF;Uetani,Tadayuki;Matsubara,Tatsuaki
有人认为镁缺乏与许多疾病有关。进行了 31 P NMR 实验，以研究无二价阳离子条件下 Na+ 取代对平滑肌 Mg2+ 消耗的影响。在豚鼠盲肠带中，细胞内游离 Mg2+ 浓度 ([Mg2+]i) 是根据 (1) 单独的 β-ATP 峰和 (2) β- 和 γ-ATP 峰的化学位移估算的。两种估计都表明，在无 Mg2+、无 Ca2+ 的溶液中，[Mg2+] 的减少非常缓慢，其中 Na+ 被大阳离子（例如 NMDG（N-甲基-D-葡萄糖胺）和胆碱）取代。此外，张力发展的测量结果支持了用 NMDG 替代保存细胞内 Mg2+ 的建议。用小阳离子 Li+ 取代细胞外 Na+ 也会使 β-ATP 峰向较低频率移动，但频率移动明显小于用 K+ 取代 Na+ 时所见的频率移动。然而，估计的 [Mg2+] 消耗与使用在 Li+ 基模型溶液中获得的无金属和 Mg2+ 结合 ATP 的滴定曲线用 K+ 取代 Na+ 后观察到的结果相当。结论是，只有当小阳离子为细胞外介质的主要电解质时，Mg2+才迅速减少。处理 100 分钟后，用 NMDG、胆碱或 Li+ 替代 Na+ 对细胞内 ATP 浓度几乎没有影响。
It has been suggested that magnesium deficiency is correlated with many diseases.31P NMR experiments were carried out in order to investigate the effects of Na+substitution on Mg2+depletion in smooth muscle under divalent cation‐free conditions. In the taenia of guinea‐pig caeci, the intracellular free Mg2+concentration ([Mg2+]i) was estimated from the chemical shifts of (1) the β‐ATP peak alone and (2) β‐ and γ‐ATP peaks. Both estimations indicated that [Mg2+]idecreased only very slowly in Mg2+‐free, Ca2+‐free solutions in which Na+was substituted with large cations such as NMDG (N‐methyl‐D‐glucamine) and choline. Furthermore, the measurements of tension development supported the suggestion of preservation of intracellular Mg2+with NMDG substitution. Substituting extracellular Na+with the small cation, Li+, also shifted the β‐ATP peak towards a lower frequency, but the frequency shift was significantly less than that seen upon Na+substitution with K+. The estimated [Mg2+]idepletion was, however, comparable with that seen after Na+substitution with K+using the titration curves of metal‐free and Mg2+‐bound ATP obtained in Li+‐based model solutions. It was concluded that Mg2+rapidly decreases only when small cations were the major electrolyte of the extracellular medium. Na+substitutions with NMDG, choline or Li+had little effect on intracellular ATP concentration after 100 min treatment.