Smith J B, Rozengurt E
Proc Natl Acad Sci U S A. 1978 Nov;75(11):5560-4. doi: 10.1073/pnas.75.11.5560.
Two ionophores (monensin and gramicidin) that carry Na+ into 3T3 cells markedly enhance the rate of 86Rb+ uptake. Ouabain prevents both ionophores from increasing 86Rb+ uptake, indicating that the ionophores activate the Na+,K+ pump. Measurements of 86Rb+ uptake and cell Na+ and K+ over a range of monensin concentrations show that the activity of the Na+,K+ pump in 3T3 cells is limited by the supply of internal Na+ and is extremely sensitive to small changes in internal Na+. Serum rapidly enhances the rate of 22Na+ uptake and net Na+ entry when Na+ exit is inhibited by ouabain. At 0.3 microgram/ml, monensin increases the rate of net Na+ entry and activates the Na+,K+ pump by the same degree as serum. The stimulation of 86Rb+ uptake by serum or the ionophores has an absolute requirement for external Na+. Thus, serum appears to stimulate the Na+,K+ pump in quiescent 3T3 cells by increasing its supply of Na+.
两种能将钠离子转运至3T3细胞内的离子载体(莫能菌素和短杆菌肽)显著提高了86铷离子的摄取速率。哇巴因可阻止这两种离子载体增加86铷离子的摄取,这表明离子载体激活了钠钾泵。在一系列莫能菌素浓度下对86铷离子摄取以及细胞内钠钾离子的测量结果显示,3T3细胞中钠钾泵的活性受细胞内钠离子供应的限制,并且对细胞内钠离子的微小变化极为敏感。当哇巴因抑制钠离子外流时,血清能迅速提高22钠离子的摄取速率和净钠离子内流。在0.3微克/毫升的浓度下,莫能菌素增加净钠离子内流的速率并激活钠钾泵,其程度与血清相同。血清或离子载体对86铷离子摄取的刺激绝对依赖于细胞外的钠离子。因此,血清似乎通过增加钠离子供应来刺激静止状态下3T3细胞中的钠钾泵。