Negendank W, Shaller C
Biophys J. 1984 Sep;46(3):331-42. doi: 10.1016/S0006-3495(84)84029-1.
Self-exchanges of Na and K in human lymphocytes were measured by isotopic efflux techniques. In washed cells, K exchanged in a single slow exponential fraction, but the Na exchange had a marked curvature. It was shown that the curvature was not caused by simple bulk-phase diffusion, and it was resolved into three major fractions: fast (F) (half-time, t1/2 = 2-4 min), intermediate (I) (t1/2 = 12 min), and slow (S) (t1/2 = 125 min). Each of these appeared to follow an exponential function. The I fraction contained approximately 10 mmol Na/kg cells (25-30% of normal cellular Na), was not affected by manipulations that cause lymphocytes to gain Na, and had little or no temperature dependence. The S fraction of Na in normal cells (S1) contained approximately 10 mmol Na/kg cells, had only a slight temperature dependence, and the amount and rate of S1 were independent of external K concentration (Kex). Another slow fraction (S2) appeared when the cells underwent a net gain of Na in exchange for K, and was characterized by a steep temperature dependence and a peak rate around the transition point (the point at which half of cellular K is replaced by Na) at 0.4 mM Kex. The results are discussed within context of a theory that assigns the exchange of the major part of K in its slow exponential fraction and the Na exchange in S2 to interactions of these ions with fixed anionic sites, on intracellular macromolecules, which have been shown previously to interact cooperatively in their association with K and Na.
采用同位素外流技术测量了人淋巴细胞中钠和钾的自我交换。在洗涤过的细胞中，钾以单一缓慢指数成分进行交换，但钠交换呈现出明显的曲线。结果表明，这种曲线并非由简单的体相扩散引起，它可分解为三个主要成分：快速（F）成分（半衰期(t_{1/2}=2 - 4)分钟）、中间（I）成分（(t_{1/2}=12)分钟）和缓慢（S）成分（(t_{1/2}=125)分钟）'。这些成分中的每一个似乎都遵循指数函数。I成分含有约(10)毫摩尔钠/千克细胞（占正常细胞内钠的(25 - 30%)），不受导致淋巴细胞摄取钠的操作影响，且几乎没有温度依赖性。正常细胞中钠的S成分（(S1)）含有约(10)毫摩尔钠/千克细胞，只有轻微的温度依赖性，(S1)的量和速率与细胞外钾浓度（(K_{ex})）无关。当细胞经历钠与钾的净交换并摄取钠时，出现另一个缓慢成分（(S2)），其特征是具有陡峭的温度依赖性，并且在(0.4)毫摩尔(K_{ex})时，在转变点（细胞内一半钾被钠取代的点）附近有一个峰值速率。本文在一个理论框架内讨论了这些结果，该理论将钾的主要缓慢指数成分的交换以及(S2)中钠的交换归因于这些离子与细胞内大分子上固定阴离子位点的相互作用，此前已证明这些位点在与钾和钠的结合中存在协同作用。
