叠氮化物和高细胞内钠离子浓度对钠泵的刺激作用：泵位点数量和周转率的变化

Stimulation of the sodium pump by azide and high internal sodium: changes in the number of pumping sites and turnover rate.

Erlij D, Grinstein S

J Physiol. 1976 Jul;259(1):33-45. doi: 10.1113/jphysiol.1976.sp011453.

Abstract

The effects of 5 mM azide on [3H]ouabain uptake and 22Na efflux were determined. Both glycoside uptake and 22Na efflux were enhanced by azide. 2. Azide stimulated the Na pump in muscles whose pumping sites had been inhibited by ouabain and then transferred to a glycoside-free solution. This stimulation was observed before detecting any recovery of the initial pumping activity. 3. When both the resting and the azide-stimulated 22Na efflux had been blocked by ouabain, an additional exposure to azide, in a ouabain-free solution, had no further effects on 22Na efflux. 4. It is concluded that the increase in Na pumping caused by azide is due in part to an increase in the number of pumping sites. 5. [3H]ouabain binding was measured in muscles with different intracellular alkali cation concentrations. Variations in [Na]i from 15 up to 50 mM did not significantly affect the amount of glycoside bound. A substantial increase in binding occurred when [Na]i reached 70 mM. 6. It is proposed that the increase in Na extrusion that occurs during the recovery of Na loaded muscles mostly results from an increased turnover rate of the pump rather than from an increase in number of pumping sites.

摘要

测定了5 mM叠氮化物对[³H]哇巴因摄取及²²Na外流的影响。叠氮化物使糖苷摄取和²²Na外流均增强。
叠氮化物刺激了那些其泵浦位点已被哇巴因抑制然后转移至无糖苷溶液中的肌肉中的钠泵。在检测到初始泵浦活性的任何恢复之前就观察到了这种刺激。
当静息和叠氮化物刺激的²²Na外流均被哇巴因阻断时，在无哇巴因溶液中再次暴露于叠氮化物对²²Na外流没有进一步影响。
得出结论，叠氮化物引起的钠泵浦增加部分归因于泵浦位点数量的增加。
在具有不同细胞内碱金属阳离子浓度的肌肉中测量了[³H]哇巴因结合。细胞内[Na]从15 mM增加到50 mM对结合的糖苷量没有显著影响。当细胞内[Na]达到70 mM时结合显著增加。
有人提出，钠负荷肌肉恢复过程中发生的钠外流增加主要是由于泵的周转率增加而不是泵浦位点数量的增加。