Schmidt W F, McManus T J
J Gen Physiol. 1977 Jul;70(1):59-79. doi: 10.1085/jgp.70.1.59.
Duck red cells in hypertonic media experience rapid osmotic shrinkage followed by gradual reswelling back toward their original volume. This uptake of salt and water is self limiting and demands a specific ionic composition of the external solution. Although ouabain (10(-4)M) alters the pattern of cation accumulation from predominantly potassium to sodium, it does not affect the rate of the reaction, or the total amount of salt or water taken up. To study the response without the complications of active Na-K transport, ouabain was added to most incubations. All water accumulated by the cells can be accounted for by net salt uptake. Specific external cation requirements for reswelling include: sufficient sodium (more than 23 mM), and elevated potassium (more than 7 mM). In the absence of external potassium cells lose potassium without gaining sodium and continue to shrink instead of reswelling. Adding rubidium to the potassium- free solution promotes an even greater loss of cell potassium, yet causes swelling due to a net uptake of sodium and rubidium followed by chloride. The diuretic furosemide (10(-3)M) inhibits net sodium uptake which depends on potassium (or rubidium), as well as inhibits net sodium uptake which depends on sodium. As a result, cell volume is stabilized in the presence of this drug by inhibition of shrinkage, at low, and of swelling at high external potassium. The response has a high apparent energy of activation (15-20 kcal/mol). We propose that net salt and water movements in hypertonic solutions containing ouabain are mediated by direct coupling or cis-interaction, between sodium and potassium so that the uphill movement of one is driven by the downhill movement of the other in the same direction.
鸭红细胞在高渗介质中会经历快速的渗透性收缩，随后逐渐再膨胀至其原始体积。这种盐和水的摄取是自我限制的，并且需要外部溶液具有特定的离子组成。尽管哇巴因（10⁻⁴M）会改变阳离子积累模式，从主要积累钾转变为积累钠，但它并不影响反应速率，也不影响摄取的盐或水的总量。为了在没有主动钠钾转运并发症的情况下研究这种反应，在大多数孵育实验中添加了哇巴因。细胞积累的所有水分都可以通过净盐摄取来解释。再膨胀所需的特定外部阳离子包括：足够的钠（超过23 mM）和升高的钾（超过7 mM）。在没有外部钾的情况下，细胞会失去钾而不摄取钠，并继续收缩而不是再膨胀。向无钾溶液中添加铷会促进细胞钾的更大损失，但由于钠和铷随后与氯的净摄取而导致肿胀。利尿剂速尿（10⁻³M）抑制依赖钾（或铷）的净钠摄取，以及抑制依赖钠的净钠摄取。因此，在这种药物存在的情况下，通过抑制低外部钾浓度下的收缩和高外部钾浓度下的肿胀，细胞体积得以稳定。该反应具有较高的表观活化能（15 - 20千卡/摩尔）。我们提出，在含有哇巴因的高渗溶液中，净盐和水的移动是由钠和钾之间的直接偶联或顺式相互作用介导的，使得一种离子的上坡移动由另一种离子在同一方向的下坡移动驱动。
