The effects of ouabain and ethacrynic acid on the intracellular sodium and potassium concentrations in renal medullary slices incubated in cold potassium-free ringer solution and re-incubated at 37 degrees C in the presence of external potassium.
The cells in slices cut from the renal outer medulla of normally hydrated adult rats were loaded with Na and depleted of K by incubation for up to 100 min in cold iso-osmolal K-free Ringer containing 180 mM-Na. There was a continuous net cellular water loss during this time; an inverse linear relationship existed between water content and intracellular Na concentration. 2. The original intracellular Na and K concentration were restored following 60 min re-incubation in warm Ringer (37 degrees C) containing 5-9 mM-K. Restoration of cellular water content was incomplete after re-incubation for up to 120 min. 3. During incubation in cold K-free Ringer the presence of 1 mM ouabain did not affect cellular Na uptake or K and water loss. Ethacrynic acid, 1 mM, completely blocked cellular Na uptake and water loss, without affecting the intracellular K concentration at 100 min. When ouabain and ethacrynic acid were present together water loss was also prevented but intracellular Na concentration rose slightly by 100 min. 4. During re-incubation in warm K-containing Ringer 1 mM ouabain inhibited Na extrusion completely for up to 60 min while only partially preventing K uptake and further depressing the level of cellular hydration. Ouabain in the presence of 1 mM ethacrynic acid had similar effects on intracellular Na and K concentrations, but raised the level of intracellular water above that of cells in control slices. 5. Ethacrynic acid alone, 1 mM, did not interfere with Na extrusion or K uptake, but also raised intracellular water above control values. 6. The results obtained are discussed in relation to (a) the nature of the preparation used, (b) the possible membrane transport processes occurring and their known or suggested sensitivity to ouabain and ethacrynic acid, (c) the mechanisms which may be responsible for cell volume maintenance in the medulla.
摘要
将正常水合成年大鼠肾外髓切片中的细胞置于含180 mM - Na的冷等渗无钾林格液中孵育长达100分钟，使其负载Na并耗尽K。在此期间细胞持续净失水；含水量与细胞内Na浓度之间存在反线性关系。2. 在含5 - 9 mM - K的温林格液（37℃）中再孵育60分钟后，细胞内原始的Na和K浓度得以恢复。再孵育长达120分钟后，细胞含水量的恢复并不完全。3. 在冷无钾林格液中孵育期间，1 mM哇巴因不影响细胞对Na的摄取或K及水的丢失。1 mM依他尼酸完全阻断细胞对Na的摄取和水的丢失，在100分钟时不影响细胞内K浓度。当哇巴因和依他尼酸同时存在时，水的丢失也被阻止，但到100分钟时细胞内Na浓度略有升高。4. 在含K的温林格液中再孵育期间，1 mM哇巴因在长达60分钟内完全抑制Na的排出，同时仅部分阻止K的摄取并进一步降低细胞水合水平。在1 mM依他尼酸存在的情况下，哇巴因对细胞内Na和K浓度有类似影响，但使细胞内水水平高于对照切片中的细胞。5. 单独使用1 mM依他尼酸不干扰Na的排出或K的摄取，但也使细胞内水高于对照值。6. 结合以下方面对所得结果进行了讨论：(a)所用制剂的性质；(b)可能发生的膜转运过程及其对哇巴因和依他尼酸已知或推测的敏感性；(c)可能负责髓质细胞体积维持的机制。
